HTML5

manifest

DOM interface:

interface HTMLHtmlElement : HTMLElement {};

The html element represents the root of an HTML document.

The manifest attribute gives the address of the document's application cache manifest, if there is one. If the attribute is present, the attribute's value must be a valid URL.

The manifest attribute only has an effect during the early stages of document load. Changing the attribute dynamically thus has no effect (and thus, no DOM API is provided for this attribute).

For the purposes of application cache selection, later base elements cannot affect the resolving of relative URLs in manifest attributes, as the attributes are processed before those elements are seen.

The window.applicationCache IDL attribute provides scripted access to the offline application cache mechanism.

The html element in the following example declares that the document's language is English.

<!DOCTYPE html>
<html lang="en">
<head>
<title>Swapping Songs</title>
</head>
<body>
<h1>Swapping Songs</h1>
<p>Tonight I swapped some of the songs I wrote with some friends, who
gave me some of the songs they wrote. I love sharing my music.</p>
</body>
</html>

4.2 Document metadata

Status: Last call for comments

4.2.1 The `head` element

Status: Last call for comments. ISSUE-55 (head-profile) blocks progress to Last Call

Categories

None.

Contexts in which this element may be used:

As the first element in an html element.

Content model:

If the document is an iframe srcdoc document or if title information is available from a higher-level protocol: Zero or more elements of metadata content.

Otherwise: One or more elements of metadata content, of which exactly one is a title element.

Content attributes:

DOM interface:

interface HTMLHeadElement : HTMLElement {};

The head element represents a collection of metadata for the Document.

The collection of metadata in a head element can be large or small. Here is an example of a very short one:

<!doctype html>
<html>
 <head>
  <title>A document with a short head</title>
 </head>
 <body>
 ...

Here is an example of a longer one:

<!DOCTYPE HTML>
<HTML>
 <HEAD>
  <META CHARSET="UTF-8">
  <BASE HREF="http://www.example.com/">
  <TITLE>An application with a long head</TITLE>
  <LINK REL="STYLESHEET" HREF="default.css">
  <LINK REL="STYLESHEET ALTERNATE" HREF="big.css" TITLE="Big Text">
  <SCRIPT SRC="support.js"></SCRIPT>
  <META NAME="APPLICATION-NAME" CONTENT="Long headed application">
 </HEAD>
 <BODY>
 ...

The title element is a required child in most situations, but when a higher-level protocol provides title information, e.g. in the Subject line of an e-mail when HTML is used as an e-mail authoring format, the title element can be omitted.

4.2.2 The `title` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

In a head element containing no other title elements.

Content model:

Text.

Content attributes:

DOM interface:

interface HTMLTitleElement : HTMLElement {
           attribute DOMString text;
};

The title element represents the document's title or name. Authors should use titles that identify their documents even when they are used out of context, for example in a user's history or bookmarks, or in search results. The document's title is often different from its first heading, since the first heading does not have to stand alone when taken out of context.

There must be no more than one title element per document.

title . text [ = value ]

Returns the contents of the element, ignoring child nodes that aren't text nodes.

Can be set, to replace the element's children with the given value.

The IDL attribute text must return a concatenation of the contents of all the text nodes that are direct children of the title element (ignoring any other nodes such as comments or elements), in tree order. On setting, it must act the same way as the textContent IDL attribute.

Here are some examples of appropriate titles, contrasted with the top-level headings that might be used on those same pages.

  <title>Introduction to The Mating Rituals of Bees</title>
    ...
  <h1>Introduction</h1>
  <p>This companion guide to the highly successful
  <cite>Introduction to Medieval Bee-Keeping</cite> book is...

The next page might be a part of the same site. Note how the title describes the subject matter unambiguously, while the first heading assumes the reader knows what the context is and therefore won't wonder if the dances are Salsa or Waltz:

  <title>Dances used during bee mating rituals</title>
    ...
  <h1>The Dances</h1>

The string to use as the document's title is given by the document.title IDL attribute. User agents should use the document's title when referring to the document in their user interface.

4.2.3 The `base` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

In a head element containing no other base elements.

Content model:

Empty.

Content attributes:

href

target

DOM interface:

interface HTMLBaseElement : HTMLElement {
           attribute DOMString href;
           attribute DOMString target;
};

The base element allows authors to specify the document base URL for the purposes of resolving relative URLs, and the name of the default browsing context for the purposes of following hyperlinks. The element does not represent any content beyond this information.

There must be no more than one base element per document.

A base element must have either an href attribute, a target attribute, or both.

The href content attribute, if specified, must contain a valid URL.

A base element, if it has an href attribute, must come before any other elements in the tree that have attributes defined as taking URLs, except the html element (its manifest attribute isn't affected by base elements).

If there are multiple base elements with href attributes, all but the first are ignored.

The target attribute, if specified, must contain a valid browsing context name or keyword, which specifies which browsing context is to be used as the default when hyperlinks and forms in the Document cause navigation.

A base element, if it has a target attribute, must come before any elements in the tree that represent hyperlinks.

If there are multiple base elements with target attributes, all but the first are ignored.

The href and target IDL attributes must reflect the respective content attributes of the same name.

In this example, a base element is used to set the document base URL:

<!DOCTYPE html>
<html>
    <head>
        <title>This is an example for the &lt;base&gt; element</title>
        <base href="http://www.example.com/news/index.html">
    </head>
    <body>
        <p>Visit the <a href="archives.html">archives</a>.</p>
    </body>
</html>

The link in the above example would be a link to "http://www.example.com/news/archives.html".

4.2.4 The `link` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where metadata content is expected.

In a noscript element that is a child of a head element.

Content model:

Empty.

Content attributes:

href

rel

media

hreflang

type

sizes

Also, the title attribute has special semantics on this element.

DOM interface:

interface HTMLLinkElement : HTMLElement {
           attribute boolean disabled;
           attribute DOMString href;
           attribute DOMString rel;
  readonly attribute DOMTokenList relList;
           attribute DOMString media;
           attribute DOMString hreflang;
           attribute DOMString type;
  [PutForwards=value] readonly attribute DOMSettableTokenList sizes;
};
HTMLLinkElement implements LinkStyle;

The link element allows authors to link their document to other resources.

The destination of the link(s) is given by the href attribute, which must be present and must contain a valid URL. If the href attribute is absent, then the element does not define a link.

A link element must have rel attribute.

The types of link indicated (the relationships) are given by the value of the rel attribute, which, if present, must have a value that is a set of space-separated tokens. The allowed values and their meanings are defined in a later section. If the rel attribute is absent, or if the values used are not allowed according to the definitions in this specification, then the element does not define a link.

Two categories of links can be created using the link element. Links to external resources are links to resources that are to be used to augment the current document, and hyperlink links are links to other documents. The link types section defines whether a particular link type is an external resource or a hyperlink. One element can create multiple links (of which some might be external resource links and some might be hyperlinks); exactly which and how many links are created depends on the keywords given in the rel attribute. User agents must process the links on a per-link basis, not a per-element basis.

Each link is handled separately. For instance, if there are two link elements with rel="stylesheet", they each count as a separate external resource, and each is affected by its own attributes independently.

The exact behavior for links to external resources depends on the exact relationship, as defined for the relevant link type. Some of the attributes control whether or not the external resource is to be applied (as defined below). For external resources that are represented in the DOM (for example, style sheets), the DOM representation must be made available even if the resource is not applied. To obtain the resource, the user agent must resolve the URL given by the href attribute, relative to the element, and then fetch the resulting absolute URL. User agents may opt to only try to obtain such resources when they are needed, instead of pro-actively fetching all the external resources that are not applied.

The semantics of the protocol used (e.g. HTTP) must be followed when fetching external resources. (For example, redirects will be followed and 404 responses will cause the external resource to not be applied.)

Once the attempts to obtain the resource and its critical subresources are complete, the user agent must, if the loads were successful, queue a task to fire a simple event named load at the link element, or, if the resource or one of its critical subresources failed to completely load for any reason (e.g. DNS error, HTTP 404 response, a connection being prematurely closed, unsupported Content-Type), queue a task to fire a simple event named error at the link element. Non-network errors in processing the resource or its subresources (e.g. CSS parse errors, PNG decoding errors) are not failures for the purposes of this paragraph.

The task source for these tasks is the DOM manipulation task source.

The element must delay the load event of the element's document until all the attempts to obtain the resource and its critical subresources are complete. (Resources that the user agent has not yet attempted to obtain, e.g. because it is waiting for the resource to be needed, do not delay the load event.)

Which resources are considered critical or not is defined by the relevant specification. For CSS resources, only @import rules introduce critical subresources; other resources, e.g. fonts or backgrounds, are not.

Interactive user agents may provide users with a means to follow the hyperlinks created using the link element, somewhere within their user interface. The exact interface is not defined by this specification, but it could include the following information (obtained from the element's attributes, again as defined below), in some form or another (possibly simplified), for each hyperlink created with each link element in the document:

The relationship between this document and the resource (given by the rel attribute)
The title of the resource (given by the title attribute).
The address of the resource (given by the href attribute).
The language of the resource (given by the hreflang attribute).
The optimum media for the resource (given by the media attribute).

User agents could also include other information, such as the type of the resource (as given by the type attribute).

Hyperlinks created with the link element and its rel attribute apply to the whole page. This contrasts with the rel attribute of a and area elements, which indicates the type of a link whose context is given by the link's location within the document.

The media attribute says which media the resource applies to. The value must be a valid media query.

If the link is a hyperlink then the media attribute is purely advisory, and describes for which media the document in question was designed.

However, if the link is an external resource link, then the media attribute is prescriptive. The user agent must apply the external resource to a view when the media attribute's value matches the environment of that view and the other relevant conditions apply, and must not apply it otherwise.

The external resource might have further restrictions defined within that limit its applicability. For example, a CSS style sheet might have some @media blocks. This specification does not override such further restrictions or requirements.

The default, if the media attribute is omitted, is "all", meaning that by default links apply to all media.

The hreflang attribute on the link element has the same semantics as the hreflang attribute on hyperlink elements.

The type attribute gives the MIME type of the linked resource. It is purely advisory. The value must be a valid MIME type.

For external resource links, the type attribute is used as a hint to user agents so that they can avoid fetching resources they do not support. If the attribute is present, then the user agent must assume that the resource is of the given type (even if that is not a valid MIME type, e.g. the empty string). If the attribute is omitted, but the external resource link type has a default type defined, then the user agent must assume that the resource is of that type. If the UA does not support the given MIME type for the given link relationship, then the UA should not obtain the resource; if the UA does support the given MIME type for the given link relationship, then the UA should obtain the resource. If the attribute is omitted, and the external resource link type does not have a default type defined, but the user agent would obtain the resource if the type was known and supported, then the user agent should obtain the resource under the assumption that it will be supported.

User agents must not consider the type attribute authoritative — upon fetching the resource, user agents must not use the type attribute to determine its actual type. Only the actual type (as defined in the next paragraph) is used to determine whether to apply the resource, not the aforementioned assumed type.

If the external resource link type defines rules for processing the resource's Content-Type metadata, then those rules apply. Otherwise, if the resource is expected to be an image, user agents may apply the image sniffing rules, with the official type being the type determined from the resource's Content-Type metadata, and use the resulting sniffed type of the resource as if it was the actual type. Otherwise, if neither of these conditions apply or if the user agent opts not to apply the image sniffing rules, then the user agent must use the resource's Content-Type metadata to determine the type of the resource. If there is no type metadata, but the external resource link type has a default type defined, then the user agent must assume that the resource is of that type.

The stylesheet link type defines rules for processing the resource's Content-Type metadata.

Once the user agent has established the type of the resource, the user agent must apply the resource if it is of a supported type and the other relevant conditions apply, and must ignore the resource otherwise.

If a document contains style sheet links labeled as follows:

<link rel="stylesheet" href="A" type="text/plain">
<link rel="stylesheet" href="B" type="text/css">
<link rel="stylesheet" href="C">

...then a compliant UA that supported only CSS style sheets would fetch the B and C files, and skip the A file (since text/plain is not the MIME type for CSS style sheets).

For files B and C, it would then check the actual types returned by the server. For those that are sent as text/css, it would apply the styles, but for those labeled as text/plain, or any other type, it would not.

If one of the two files was returned without a Content-Type metadata, or with a syntactically incorrect type like Content-Type: "null", then the default type for stylesheet links would kick in. Since that default type is text/css, the style sheet would nonetheless be applied.

The title attribute gives the title of the link. With one exception, it is purely advisory. The value is text. The exception is for style sheet links, where the title attribute defines alternative style sheet sets.

The title attribute on link elements differs from the global title attribute of most other elements in that a link without a title does not inherit the title of the parent element: it merely has no title.

The sizes attribute is used with the icon link type. The attribute must not be specified on link elements that do not have a rel attribute that specifies the icon keyword.

Some versions of HTTP defined a Link: header, to be processed like a series of link elements. If supported, for the purposes of ordering links defined by HTTP headers must be assumed to come before any links in the document, in the order that they were given in the HTTP entity header. (URIs in these headers are to be processed and resolved according to the rules given in HTTP; the rules of this specification don't apply.) [HTTP] [WEBLINK]

The IDL attributes href, rel, media, hreflang, and type, and sizes each must reflect the respective content attributes of the same name.

The IDL attribute relList must reflect the rel content attribute.

The IDL attribute disabled only applies to style sheet links. When the link element defines a style sheet link, then the disabled attribute behaves as defined for the alternative style sheets DOM. For all other link elements it always return false and does nothing on setting.

The LinkStyle interface is also implemented by this element; the styling processing model defines how. [CSSOM]

Here, a set of link elements provide some style sheets:

<!-- a persistent style sheet -->
<link rel="stylesheet" href="default.css">

<!-- the preferred alternate style sheet -->
<link rel="stylesheet" href="green.css" title="Green styles">

<!-- some alternate style sheets -->
<link rel="alternate stylesheet" href="contrast.css" title="High contrast">
<link rel="alternate stylesheet" href="big.css" title="Big fonts">
<link rel="alternate stylesheet" href="wide.css" title="Wide screen">

The following example shows how you can specify versions of the page that use alternative formats, are aimed at other languages, and that are intended for other media:

<link rel=alternate href="/en/html" hreflang=en type=text/html title="English HTML">
<link rel=alternate href="/fr/html" hreflang=fr type=text/html title="French HTML">
<link rel=alternate href="/en/html/print" hreflang=en type=text/html media=print title="English HTML (for printing)">
<link rel=alternate href="/fr/html/print" hreflang=fr type=text/html media=print title="French HTML (for printing)">
<link rel=alternate href="/en/pdf" hreflang=en type=application/pdf title="English PDF">
<link rel=alternate href="/fr/pdf" hreflang=fr type=application/pdf title="French PDF">

4.2.5 The `meta` element

Status: Last call for comments. ISSUE-99 (meta-scheme) blocks progress to Last Call

Categories

Contexts in which this element may be used:

If the charset attribute is present, or if the element's http-equiv attribute is in the Encoding declaration state: in a head element.

If the http-equiv attribute is present but not in the Encoding declaration state: in a head element.

If the http-equiv attribute is present but not in the Encoding declaration state: in a noscript element that is a child of a head element.

If the name attribute is present: where metadata content is expected.

Content model:

Empty.

Content attributes:

name

http-equiv

content

charset

DOM interface:

interface HTMLMetaElement : HTMLElement {
           attribute DOMString name;
           attribute DOMString httpEquiv;
           attribute DOMString content;
};

The meta element represents various kinds of metadata that cannot be expressed using the title, base, link, style, and script elements.

The meta element can represent document-level metadata with the name attribute, pragma directives with the http-equiv attribute, and the file's character encoding declaration when an HTML document is serialized to string form (e.g. for transmission over the network or for disk storage) with the charset attribute.

Exactly one of the name, http-equiv, and charset attributes must be specified.

If either name or http-equiv is specified, then the content attribute must also be specified. Otherwise, it must be omitted.

The charset attribute specifies the character encoding used by the document. This is a character encoding declaration. If the attribute is present in an XML document, its value must be an ASCII case-insensitive match for the string "UTF-8" (and the document is therefore forced to use UTF-8 as its encoding).

The charset attribute on the meta element has no effect in XML documents, and is only allowed in order to facilitate migration to and from XHTML.

There must not be more than one meta element with a charset attribute per document.

The content attribute gives the value of the document metadata or pragma directive when the element is used for those purposes. The allowed values depend on the exact context, as described in subsequent sections of this specification.

If a meta element has a name attribute, it sets document metadata. Document metadata is expressed in terms of name/value pairs, the name attribute on the meta element giving the name, and the content attribute on the same element giving the value. The name specifies what aspect of metadata is being set; valid names and the meaning of their values are described in the following sections. If a meta element has no content attribute, then the value part of the metadata name/value pair is the empty string.

The name and content IDL attributes must reflect the respective content attributes of the same name. The IDL attribute httpEquiv must reflect the content attribute http-equiv.

4.2.5.1 Standard metadata names

Status: Last call for comments. ISSUE-79 (meta-keywords) blocks progress to Last Call

This specification defines a few names for the name attribute of the meta element.

Names are case-insensitive, and must be compared in an ASCII case-insensitive manner.

application-name

The value must be a short free-form string giving the name of the Web application that the page represents. If the page is not a Web application, the application-name metadata name must not be used. There must not be more than one meta element with its name attribute set to the value application-name per document. User agents may use the application name in UI in preference to the page's title, since the title might include status messages and the like relevant to the status of the page at a particular moment in time instead of just being the name of the application.

author

The value must be a free-form string giving the name of one of the page's authors.

description

The value must be a free-form string that describes the page. The value must be appropriate for use in a directory of pages, e.g. in a search engine. There must not be more than one meta element with its name attribute set to the value description per document.

generator

The value must be a free-form string that identifies one of the software packages used to generate the document. This value must not be used on hand-authored pages.

Here is what a tool called "Frontweaver" could include in its output, in the page's head element, to identify itself as the tool used to generate the page:

<meta name=generator content="Frontweaver 8.2">

4.2.5.2 Other metadata names

Status: Last call for comments. ISSUE-27 (rel-ownership) and ISSUE-102 (meta-name-registry) block progress to Last Call

Extensions to the predefined set of metadata names may be registered in the WHATWG Wiki MetaExtensions page. [WHATWGWIKI]

Anyone is free to edit the WHATWG Wiki MetaExtensions page at any time to add a type. These new names must be specified with the following information:

Keyword

The actual name being defined. The name should not be confusingly similar to any other defined name (e.g. differing only in case).

Brief description

A short non-normative description of what the metadata name's meaning is, including the format the value is required to be in.

Specification

A link to a more detailed description of the metadata name's semantics and requirements. It could be another page on the Wiki, or a link to an external page.

Synonyms

A list of other names that have exactly the same processing requirements. Authors should not use the names defined to be synonyms, they are only intended to allow user agents to support legacy content. Anyone may remove synonyms that are not used in practice; only names that need to be processed as synonyms for compatibility with legacy content are to be registered in this way.

Status

One of the following:

Proposed: The name has not received wide peer review and approval. Someone has proposed it and is, or soon will be, using it.
Ratified: The name has received wide peer review and approval. It has a specification that unambiguously defines how to handle pages that use the name, including when they use it in incorrect ways.
Discontinued: The metadata name has received wide peer review and it has been found wanting. Existing pages are using this metadata name, but new pages should avoid it. The "brief description" and "specification" entries will give details of what authors should use instead, if anything.

If a metadata name is found to be redundant with existing values, it should be removed and listed as a synonym for the existing value.

If a metadata name is registered in the "proposed" state for a period of a month or more without being used or specified, then it may be removed from the registry.

If a metadata name is added with the "proposed" status and found to be redundant with existing values, it should be removed and listed as a synonym for the existing value. If a metadata name is added with the "proposed" status and found to be harmful, then it should be changed to "discontinued" status.

Anyone can change the status at any time, but should only do so in accordance with the definitions above.

Conformance checkers must use the information given on the WHATWG Wiki MetaExtensions page to establish if a value is allowed or not: values defined in this specification or marked as "proposed" or "ratified" must be accepted, whereas values marked as "discontinued" or not listed in either this specification or on the aforementioned page must be rejected as invalid. Conformance checkers may cache this information (e.g. for performance reasons or to avoid the use of unreliable network connectivity).

When an author uses a new metadata name not defined by either this specification or the Wiki page, conformance checkers should offer to add the value to the Wiki, with the details described above, with the "proposed" status.

Metadata names whose values are to be URLs must not be proposed or accepted. Links must be represented using the link element, not the meta element.

4.2.5.3 Pragma directives

Status: Last call for comments

When the http-equiv attribute is specified on a meta element, the element is a pragma directive.

The http-equiv attribute is an enumerated attribute. The following table lists the keywords defined for this attribute. The states given in the first cell of the rows with keywords give the states to which those keywords map.

State	Keywords	Notes
Content Language	`content-language`	Conformance checkers will include a warning
Encoding declaration	`content-type`
Default style	`default-style`
Refresh	`refresh`

When a meta element is inserted into the document, if its http-equiv attribute is present and represents one of the above states, then the user agent must run the algorithm appropriate for that state, as described in the following list:

Content language state (http-equiv="content-language")

This pragma sets the pragma-set default language. Until the pragma is successfully processed, there is no pragma-set default language.

Conformance checkers will include a warning if this pragma is used. Authors are encouraged to use the lang attribute instead.

If another meta element with an http-equiv attribute in the Content Language state has already been successfully processed (i.e. when it was inserted the user agent processed it and reached the last step of this list of steps), then abort these steps.
If the meta element has no content attribute, or if that attribute's value is the empty string, then abort these steps.
If the element's content attribute contains a U+002C COMMA character (,) then abort these steps.
Let input be the value of the element's content attribute.
Let position point at the first character of input.
Skip whitespace.
Collect a sequence of characters that are not space characters.
Let the pragma-set default language be the string that resulted from the previous step.

For meta elements with an http-equiv attribute in the Content Language state, the content attribute must have a value consisting of a valid BCP 47 language code. [BCP47]

This pragma is not exactly equivalent to the HTTP Content-Language header, for instance it only supports one language. [HTTP]

Encoding declaration state (http-equiv="content-type")

The Encoding declaration state is just an alternative form of setting the charset attribute: it is a character encoding declaration. This state's user agent requirements are all handled by the parsing section of the specification.

For meta elements with an http-equiv attribute in the Encoding declaration state, the content attribute must have a value that is an ASCII case-insensitive match for a string that consists of: the literal string "text/html;", optionally followed by any number of space characters, followed by the literal string "charset=", followed by the character encoding name of the character encoding declaration.

If the document contains a meta element with an http-equiv attribute in the Encoding declaration state, then the document must not contain a meta element with the charset attribute present.

The Encoding declaration state may be used in HTML documents, but elements with an http-equiv attribute in that state must not be used in XML documents.

Default style state (http-equiv="default-style")

This pragma sets the name of the default alternative style sheet set.

If the meta element has no content attribute, or if that attribute's value is the empty string, then abort these steps.
Set the preferred style sheet set to the value of the element's content attribute. [CSSOM]

Refresh state (http-equiv="refresh")

This pragma acts as timed redirect.

If another meta element with an http-equiv attribute in the Refresh state has already been successfully processed (i.e. when it was inserted the user agent processed it and reached the last step of this list of steps), then abort these steps.
If the meta element has no content attribute, or if that attribute's value is the empty string, then abort these steps.
Let input be the value of the element's content attribute.
Let position point at the first character of input.
Skip whitespace.
Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), and parse the resulting string using the rules for parsing non-negative integers. If the sequence of characters collected is the empty string, then no number will have been parsed; abort these steps. Otherwise, let time be the parsed number.
Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9) and U+002E FULL STOP (.). Ignore any collected characters.
Skip whitespace.
Let url be the address of the current page.
If the character in input pointed to by position is a U+003B SEMICOLON (";"), then advance position to the next character. Otherwise, jump to the last step.
Skip whitespace.
If the character in input pointed to by position is a U+0055 LATIN CAPITAL LETTER U character (U) or a U+0075 LATIN SMALL LETTER U character (u), then advance position to the next character. Otherwise, jump to the last step.
If the character in input pointed to by position is a U+0052 LATIN CAPITAL LETTER R character (R) or a U+0072 LATIN SMALL LETTER R character (r), then advance position to the next character. Otherwise, jump to the last step.
If the character in input pointed to by position is s U+004C LATIN CAPITAL LETTER L character (L) or a U+006C LATIN SMALL LETTER L character (l), then advance position to the next character. Otherwise, jump to the last step.
Skip whitespace.
If the character in input pointed to by position is a U+003D EQUALS SIGN ("="), then advance position to the next character. Otherwise, jump to the last step.
Skip whitespace.
If the character in input pointed to by position is either a U+0027 APOSTROPHE character (') or U+0022 QUOTATION MARK character ("), then let quote be that character, and advance position to the next character. Otherwise, let quote be the empty string.
Let url be equal to the substring of input from the character at position to the end of the string.
If quote is not the empty string, and there is a character in url equal to quote, then truncate url at that character, so that it and all subsequent characters are removed.
Strip any trailing space characters from the end of url.
Strip any U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), and U+000D CARRIAGE RETURN (CR) characters from url.
Resolve the url value to an absolute URL, relative to the meta element. If this fails, abort these steps.
Perform one or more of the following steps:
- Set a timer so that in time seconds, adjusted to take into account user or user agent preferences, if the user has not canceled the redirect, the user agent navigates the document's browsing context to url, with replacement enabled, and with the document's browsing context as the source browsing context.
- Provide the user with an interface that, when selected, navigates a browsing context to url, with the document's browsing context as the source browsing context.
- Do nothing.
In addition, the user agent may, as with anything, inform the user of any and all aspects of its operation, including the state of any timers, the destinations of any timed redirects, and so forth.

For meta elements with an http-equiv attribute in the Refresh state, the content attribute must have a value consisting either of:

just a valid non-negative integer, or
a valid non-negative integer, followed by a U+003B SEMICOLON character (;), followed by one or more space characters, followed by either a U+0055 LATIN CAPITAL LETTER U character (U) or a U+0075 LATIN SMALL LETTER U character (u), a U+0052 LATIN CAPITAL LETTER R character (R) or a U+0072 LATIN SMALL LETTER R character (r), a U+004C LATIN CAPITAL LETTER L character (L) or a U+006C LATIN SMALL LETTER L character (l), a U+003D EQUALS SIGN character (=), and then a valid URL.

In the former case, the integer represents a number of seconds before the page is to be reloaded; in the latter case the integer represents a number of seconds before the page is to be replaced by the page at the given URL.

A news organization's front page could include the following markup in the page's head element, to ensure that the page automatically reloads from the server every five minutes:

<meta http-equiv="Refresh" content="300">

A sequence of pages could be used as an automated slide show by making each page refresh to the next page in the sequence, using markup such as the following:

<meta http-equiv="Refresh" content="20; URL=page4.html">

There must not be more than one meta element with any particular state in the document at a time.

4.2.5.4 Other pragma directives

Status: Last call for comments

Extensions to the predefined set of pragma directives may, under certain conditions, be registered in the WHATWG Wiki PragmaExtensions page. [WHATWGWIKI]

Such extensions must use a name that is identical to an HTTP header registered in the Permanent Message Header Field Registry, and must have behavior identical to that described for the HTTP header. [IANAPERMHEADERS]

Pragma directives corresponding to headers describing metadata, or not requiring specific user agent processing, must not be registered; instead, use metadata names. Pragma directives corresponding to headers that affect the HTTP processing model (e.g. caching) must not be registered, as they would result in HTTP-level behavior being different for user agents that implement HTML than for user agents that do not.

Anyone is free to edit the WHATWG Wiki PragmaExtensions page at any time to add a pragma directive satisfying these conditions. Such registrations must specify the following information:

Keyword: The actual name being defined. The name must match a previously-registered HTTP name with the same requirements.
Brief description: A short non-normative description of the purpose of the pragma directive.
Specification: A link to the specification defining the corresponding HTTP header.

Conformance checkers must use the information given on the WHATWG Wiki PragmaExtensions page to establish if a value is allowed or not: values defined in this specification or listed on the aforementioned page must be accepted, whereas values not listed in either this specification or on the aforementioned page must be rejected as invalid. Conformance checkers may cache this information (e.g. for performance reasons or to avoid the use of unreliable network connectivity).

4.2.5.5 Specifying the document's character encoding

Status: Last call for comments

A character encoding declaration is a mechanism by which the character encoding used to store or transmit a document is specified.

The following restrictions apply to character encoding declarations:

The character encoding name given must be the name of the character encoding used to serialize the file.
The value must be a valid character encoding name, and must be an ASCII case-insensitive match for the preferred MIME name for that encoding. [IANACHARSET]
The character encoding declaration must be serialized without the use of character references or character escapes of any kind.
The element containing the character encoding declaration must be serialized completely within the first 512 bytes of the document.
There can only be one character encoding declaration in the document.

If an HTML document does not start with a BOM, and if its encoding is not explicitly given by Content-Type metadata, and the document is not an iframe srcdoc document, then the character encoding used must be an ASCII-compatible character encoding, and, in addition, if that encoding isn't US-ASCII itself, then the encoding must be specified using a meta element with a charset attribute or a meta element with an http-equiv attribute in the Encoding declaration state.

If the document is an iframe srcdoc document, the document must not have a character encoding declaration. (In this case, the source is already decoded, since it is part of the document that contained the iframe.)

If an HTML document contains a meta element with a charset attribute or a meta element with an http-equiv attribute in the Encoding declaration state, then the character encoding used must be an ASCII-compatible character encoding.

Authors are encouraged to use UTF-8. Conformance checkers may advise authors against using legacy encodings.

Authoring tools should default to using UTF-8 for newly-created documents.

Encodings in which a series of bytes in the range 0x20 to 0x7E can encode characters other than the corresponding characters in the range U+0020 to U+007E represent a potential security vulnerability: a user agent that does not support the encoding (or does not support the label used to declare the encoding, or does not use the same mechanism to detect the encoding of unlabelled content as another user agent) might end up interpreting technically benign plain text content as HTML tags and JavaScript. For example, this applies to encodings in which the bytes corresponding to "<script>" in ASCII can encode a different string. Authors should not use such encodings, which are known to include JIS_C6226-1983, JIS_X0212-1990, HZ-GB-2312, JOHAB (Windows code page 1361), encodings based on ISO-2022, and encodings based on EBCDIC. Furthermore, authors must not use the CESU-8, UTF-7, BOCU-1 and SCSU encodings, which also fall into this category, because these encodings were never intended for use for Web content. [RFC1345] [RFC1842] [RFC1468] [RFC2237] [RFC1554] [RFC1922] [RFC1557] [CESU8] [UTF7] [BOCU1] [SCSU]

Authors should not use UTF-32, as the encoding detection algorithms described in this specification intentionally do not distinguish it from UTF-16. [UNICODE]

Using non-UTF-8 encodings can have unexpected results on form submission and URL encodings, which use the document's character encoding by default.

In XHTML, the XML declaration should be used for inline character encoding information, if necessary.

In HTML, to declare that the character encoding is UTF-8, the author could include the following markup near the top of the document (in the head element):

<meta charset="utf-8">

In XML, the XML declaration would be used instead, at the very top of the markup:

<?xml version="1.0" encoding="utf-8"?>

4.2.6 The `style` element

Status: Last call for comments

Categories

If the scoped attribute is present: flow content.

Contexts in which this element may be used:

If the scoped attribute is absent: where metadata content is expected.

If the scoped attribute is absent: in a noscript element that is a child of a head element.

If the scoped attribute is present: where flow content is expected, but before any other flow content other than other style elements and inter-element whitespace.

Content model:

Depends on the value of the type attribute, but must match requirements described in prose below.

Content attributes:

media

type

scoped

Also, the title attribute has special semantics on this element.

DOM interface:

interface HTMLStyleElement : HTMLElement {
           attribute boolean disabled;
           attribute DOMString media;
           attribute DOMString type;
           attribute boolean scoped;
};
HTMLStyleElement implements LinkStyle;

The style element allows authors to embed style information in their documents. The style element is one of several inputs to the styling processing model. The element does not represent content for the user.

The type attribute gives the styling language. If the attribute is present, its value must be a valid MIME type that designates a styling language. The charset parameter must not be specified. The default, which is used if the attribute is absent, is "text/css". [RFC2318]

When examining types to determine if they support the language, user agents must not ignore unknown MIME parameters — types with unknown parameters must be assumed to be unsupported. The charset parameter must be treated as an unknown parameter for the purpose of comparing MIME types here.

The media attribute says which media the styles apply to. The value must be a valid media query. The user agent must apply the styles to a view when the media attribute's value matches the environment of that view and the other relevant conditions apply, and must not apply them otherwise.

The styles might be further limited in scope, e.g. in CSS with the use of @media blocks. This specification does not override such further restrictions or requirements.

The default, if the media attribute is omitted, is "all", meaning that by default styles apply to all media.

The scoped attribute is a boolean attribute. If set, it indicates that the styles are intended just for the subtree rooted at the style element's parent element, as opposed to the whole Document.

If the scoped attribute is present, then the user agent must apply the specified style information only to the style element's parent element (if any), and that element's child nodes. Otherwise, the specified styles must, if applied, be applied to the entire document.

The title attribute on style elements defines alternative style sheet sets. If the style element has no title attribute, then it has no title; the title attribute of ancestors does not apply to the style element. [CSSOM]

The title attribute on style elements, like the title attribute on link elements, differs from the global title attribute in that a style block without a title does not inherit the title of the parent element: it merely has no title.

The textContent of a style element must match the style production in the following ABNF, the character set for which is Unicode. [ABNF]

style         = no-c-start *( c-start no-c-end c-end no-c-start )
no-c-start    = <any string that doesn't contain a substring that matches c-start >
c-start       = "<!--"
no-c-end      = <any string that doesn't contain a substring that matches c-end >
c-end         = "-->"

All descendant elements must be processed, according to their semantics, before the style element itself is evaluated. For styling languages that consist of pure text, user agents must evaluate style elements by passing the concatenation of the contents of all the text nodes that are direct children of the style element (not any other nodes such as comments or elements), in tree order, to the style system. For XML-based styling languages, user agents must pass all the child nodes of the style element to the style system.

All URLs found by the styling language's processor must be resolved, relative to the element (or as defined by the styling language), when the processor is invoked.

Once the attempts to obtain the style sheet's critical subresources, if any, are complete, or, if the style sheet has no critical subresources, once the style sheet has been parsed and processed, the user agent must, if the loads were successful or there were none, queue a task to fire a simple event named load at the style element, or, if one of the style sheet's critical subresources failed to completely load for any reason (e.g. DNS error, HTTP 404 response, a connection being prematurely closed, unsupported Content-Type), queue a task to fire a simple event named error at the style element. Non-network errors in processing the style sheet or its subresources (e.g. CSS parse errors, PNG decoding errors) are not failures for the purposes of this paragraph.

The task source for these tasks is the DOM manipulation task source.

The element must delay the load event of the element's document until all the attempts to obtain the style sheet's critical subresources, if any, are complete.

This specification does not specify a style system, but CSS is expected to be supported by most Web browsers. [CSS]

The media, type and scoped IDL attributes must reflect the respective content attributes of the same name.

The disabled IDL attribute behaves as defined for the alternative style sheets DOM.

The LinkStyle interface is also implemented by this element; the styling processing model defines how. [CSSOM]

The following document has its emphasis styled as bright red text rather than italics text, while leaving titles of works and Latin words in their default italics. It shows how using appropriate elements enables easier restyling of documents.

<!DOCTYPE html>
<html lang="en-US">
 <head>
  <title>My favorite book</title>
  <style>
   body { color: black; background: white; }
   em { font-style: normal; color: red; }
  </style>
 </head>
 <body>
  <p>My <em>favorite</em> book of all time has <em>got</em> to be
  <cite>A Cat's Life</cite>. It is a book by P. Rahmel that talks
  about the <i lang="la">Felis Catus</i> in modern human society.</p>
 </body>
</html>

4.2.7 Styling

Status: Last call for comments

The link and style elements can provide styling information for the user agent to use when rendering the document. The DOM Styling specification specifies what styling information is to be used by the user agent and how it is to be used. [CSSOM]

The style and link elements implement the LinkStyle interface. [CSSOM]

For style elements, if the user agent does not support the specified styling language, then the sheet attribute of the element's LinkStyle interface must return null. Similarly, link elements that do not represent external resource links that contribute to the styling processing model (i.e. that do not have a stylesheet keyword in their rel attribute), and link elements whose specified resource has not yet been fetched, or is not in a supported styling language, must have their LinkStyle interface's sheet attribute return null.

Otherwise, the LinkStyle interface's sheet attribute must return a StyleSheet object with the following properties: [CSSOM]

The style sheet type: The style sheet type must be the same as the style's specified type. For style elements, this is the same as the type content attribute's value, or text/css if that is omitted. For link elements, this is the Content-Type metadata of the specified resource.
The style sheet location: For link elements, the location must be the result of resolving the URL given by the element's href content attribute, relative to the element, or the empty string if that fails. For style elements, there is no location.
The style sheet media: The media must be the same as the value of the element's media content attribute, or the empty string, if the attribute is omitted.
The style sheet title: The title must be the same as the value of the element's title content attribute, if the attribute is present and has a non-empty value. If the attribute is absent or its value is the empty string, then the style sheet does not have a title (it is the empty string). The title is used for defining alternative style sheet sets.
The style sheet alternate flag: For link elements, true if the link is an alternative stylesheet. In all other cases, false.

The same object must be returned each time.

The disabled IDL attribute on link and style elements must return false and do nothing on setting, if the sheet attribute of their LinkStyle interface is null. Otherwise, it must return the value of the StyleSheet interface's disabled attribute on getting, and forward the new value to that same attribute on setting.

The rules for handling alternative style sheets are defined in the CSS object model specification. [CSSOM]

Style sheets, whether added by a link element, a style element, an <?xml-stylesheet> PI, an HTTP Link: header, or some other mechanism, have a style sheet ready flag, which is initially unset.

When a style sheet is ready to be applied, its style sheet ready flag must be set. If the style sheet referenced no other resources (e.g. it was an internal style sheet given by a style element with no @import rules), then the style rules must be synchronously made available to script; otherwise, the style rules must only be made available to script once the event loop reaches its "update the rendering" step.

A style sheet in the context of the Document of an HTML parser or XML parser is said to be a style sheet blocking scripts if the element was created by that Document's parser, and the element is either a style element or a link element that was an external resource link that contributes to the styling processing model when the element was created by the parser, and the element's style sheet was enabled when the element was created by the parser, and the element's style sheet ready flag is not yet set, and, the last time the event loop reached step 1, the element was in that Document, and the user agent hasn't given up on that particular style sheet yet. A user agent may give up on a style sheet at any time.

4.3 Scripting

Status: Last call for comments

Scripts allow authors to add interactivity to their documents.

Authors are encouraged to use declarative alternatives to scripting where possible, as declarative mechanisms are often more maintainable, and many users disable scripting.

For example, instead of using script to show or hide a section to show more details, the details element could be used.

Authors are also encouraged to make their applications degrade gracefully in the absence of scripting support.

For example, if an author provides a link in a table header to dynamically resort the table, the link could also be made to function without scripts by requesting the sorted table from the server.

4.3.1 The `script` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where metadata content is expected.

Where phrasing content is expected.

Content model:

If there is no src attribute, depends on the value of the type attribute, but must match script content restrictions.

If there is a src attribute, the element must be either empty or contain only script documentation that also matches script content restrictions.

Content attributes:

src

async

defer

type

charset

DOM interface:

interface HTMLScriptElement : HTMLElement {
           attribute DOMString src;
           attribute boolean async;
           attribute boolean defer;
           attribute DOMString type;
           attribute DOMString charset;
           attribute DOMString text;
};

The script element allows authors to include dynamic script and data blocks in their documents. The element does not represent content for the user.

When used to include dynamic scripts, the scripts may either be embedded inline or may be imported from an external file using the src attribute. If the language is not that described by "text/javascript", then the type attribute must be present, as described below.

When used to include data blocks, the data must be embedded inline, the format of the data must be given using the type attribute, and the src attribute must not be specified.

The type attribute gives the language of the script or format of the data. If the attribute is present, its value must be a valid MIME type. The charset parameter must not be specified. The default, which is used if the attribute is absent, is "text/javascript".

The src attribute, if specified, gives the address of the external script resource to use. The value of the attribute must be a valid URL identifying a script resource of the type given by the type attribute, if the attribute is present, or of the type "text/javascript", if the attribute is absent. A resource is a script resource of a given type if that type identifies a scripting language and the resource conforms with the requirements of that language's specification.

The charset attribute gives the character encoding of the external script resource. The attribute must not be specified if the src attribute is not present. If the attribute is set, its value must be a valid character encoding name, must be an ASCII case-insensitive match for the preferred MIME name for that encoding, and must match the encoding given in the charset parameter of the Content-Type metadata of the external file, if any. [IANACHARSET]

The async and defer attributes are boolean attributes that indicate how the script should be executed.

There are three possible modes that can be selected using these attributes. If the async attribute is present, then the script will be executed asynchronously, as soon as it is available. If the async attribute is not present but the defer attribute is present, then the script is executed when the page has finished parsing. If neither attribute is present, then the script is fetched and executed immediately, before the user agent continues parsing the page. The exact processing details for these attributes are described below.

The defer attribute may be specified even if the async attribute is specified, to cause legacy Web browsers that only support defer (and not async) to fall back to the defer behavior instead of the synchronous blocking behavior that is the default.

If one or both of the defer and async attributes are specified, the src attribute must also be specified.

Changing the src, type, charset, async, and defer attributes dynamically has no direct effect; these attribute are only used at specific times described below.

A script element has several associated pieces of state.

The first is a flag indicating whether or not the script block has been "already started". Initially, script elements must have this flag unset (script blocks, when created, are not "already started"). When a script element is cloned, the "already started" flag, if set, must be propagated to the clone when it is created.

The second is a flag indicating whether the element was "parser-inserted". Initially, script elements must have this flag unset. It is set by the HTML parser and is used to handle document.write() calls.

The third is a flag indicating whether or not the script block is "ready to be parser-executed". Initially, script elements must have this flag unset (script blocks, when created, are not "ready to be parser-executed"). This flag is used only for elements that are also "parser-inserted", to let the parser know when to execute the script.

The fourth and fifth pieces of state are the script block's type and the script block's character encoding. They are determined when the script is run, based on the attributes on the element at that time.

When a script element that is neither marked as having "already started" nor marked as being "parser-inserted" experiences one of the events listed in the following list, the user agent must synchronously run the script element:

The script element gets inserted into a document.
The script element is in a Document and its child nodes are changed.
The script element is in a Document and has a src attribute set where previously the element had no such attribute.

Running a script: When a script element is to be run, the user agent must act as follows:

If either:
- the script element has a type attribute and its value is the empty string, or
- the script element has no type attribute but it has a language attribute and that attribute's value is the empty string, or
- the script element has neither a type attribute nor a language attribute, then
...let the script block's type for this script element be "text/javascript".

Otherwise, if the script element has a type attribute, let the script block's type for this script element be the value of that attribute with any leading or trailing sequences of space characters removed.

Otherwise, the element has a non-empty language attribute; let the script block's type for this script element be the concatenation of the string "text/" followed by the value of the language attribute.

The language attribute is never conforming, and is always ignored if there is a type attribute present.
If the script element has a charset attribute, then let the script block's character encoding for this script element be the encoding given by the charset attribute.

Otherwise, let the script block's character encoding for this script element be the same as the encoding of the document itself.
If the script element has a for attribute, then the user agent must abort these steps at this point. The script is not executed.
If scripting is disabled for the script element, or if the user agent does not support the scripting language given by the script block's type for this script element, then the user agent must abort these steps at this point. The script is not executed.
If the element has no src attribute, and its child nodes consist only of comment nodes and empty text nodes, then the user agent must abort these steps at this point. The script is not executed.
The user agent must set the element's "already started" flag.
If the element has a src attribute, then the value of that attribute must be resolved relative to the element, and if that is successful, the specified resource must then be fetched, from the origin of the element's Document.

For historical reasons, if the URL is a javascript: URL, then the user agent must not, despite the requirements in the definition of the fetching algorithm, actually execute the script in the URL; instead the user agent must act as if it had received an empty HTTP 400 response.

Once the resource's Content Type metadata is available, if it ever is, apply the algorithm for extracting an encoding from a Content-Type to it. If this returns an encoding, and the user agent supports that encoding, then let the script block's character encoding be that encoding.

For performance reasons, user agents may start fetching the script as soon as the attribute is set, instead, in the hope that the element will be inserted into the document. Either way, once the element is inserted into the document, the load must have started. If the UA performs such prefetching, but the element is never inserted in the document, or the src attribute is dynamically changed, then the user agent will not execute the script, and the fetching process will have been effectively wasted.
Then, the first of the following options that describes the situation must be followed:

If the element has a src attribute, and the element has a defer attribute, and the element has been flagged as "parser-inserted", and the element does not have an async attribute

The element must be added to the end of the list of scripts that will execute when the document has finished parsing.

The task that the networking task source places on the task queue once the fetching algorithm has completed must set the element's "ready to be parser-executed" flag. The parser will handle executing the script.

If the element has a src attribute, and the element has been flagged as "parser-inserted", and the element does not have an async attribute

The element is the pending parsing-blocking script. (There can only be one such script at a time.)

The task that the networking task source places on the task queue once the fetching algorithm has completed must set the element's "ready to be parser-executed" flag. The parser will handle executing the script.

If the element does not have a src attribute, but there is a style sheet blocking scripts, and the element has been flagged as "parser-inserted"

The element is the pending parsing-blocking script. (There can only be one such script at a time.)

Set the element's "ready to be parser-executed" flag. The parser will handle executing the script.

If the element has a src attribute

The element must be added to the end of the list of scripts that will execute as soon as possible.

The task that the networking task source places on the task queue once the fetching algorithm has completed must execute the script block.

Otherwise

The user agent must immediately execute the script block, even if other scripts are already executing.

Fetching an external script must delay the load event of the element's document until the task that is queued by the networking task source once the resource has been fetched (defined above) has been run.

The pending parsing-blocking script is used by the parser.

Executing a script block: When the steps above require that the script block be executed, the user agent must act as follows:

If the load resulted in an error (for example a DNS error, or an HTTP 404 error)

Executing the script block must just consist of firing a simple event named error at the element.

If the load was successful

Initialize the script block's source as follows:

If the script is from an external file and the script block's type is a text-based language

The contents of that file, interpreted as string of Unicode characters, are the script source.

For each of the rows in the following table, starting with the first one and going down, if the file has as many or more bytes available than the number of bytes in the first column, and the first bytes of the file match the bytes given in the first column, then set the script block's character encoding to the encoding given in the cell in the second column of that row, irrespective of any previous value:

Bytes in Hexadecimal Encoding
FE FF UTF-16BE
FF FE UTF-16LE
EF BB BF UTF-8
This step looks for Unicode Byte Order Marks (BOMs).

The file must then be converted to Unicode using the character encoding given by the script block's character encoding.

If the script is from an external file and the script block's type is an XML-based language

The external file is the script source. When it is later executed, it must be interpreted in a manner consistent with the specification defining the language given by the script block's type.

If the script is inline and the script block's type is a text-based language

The value of the text IDL attribute at the time the element's "already started" flag was set is the script source.

If the script is inline and the script block's type is an XML-based language

The child nodes of the script element at the time the element's "already started" flag was set are the script source.
Create a script from the script element node, using the script block's source and the script block's type.

This is where the script is compiled and actually executed.
Fire a simple event named load at the script element.

Bytes in Hexadecimal	Encoding
FE FF	UTF-16BE
FF FE	UTF-16LE
EF BB BF	UTF-8

The IDL attributes src, type, charset, async, and defer, each must reflect the respective content attributes of the same name.

script . text [ = value ]

Returns the contents of the element, ignoring child nodes that aren't text nodes.

Can be set, to replace the element's children with the given value.

The IDL attribute text must return a concatenation of the contents of all the text nodes that are direct children of the script element (ignoring any other nodes such as comments or elements), in tree order. On setting, it must act the same way as the textContent IDL attribute.

When inserted using the document.write() method, script elements execute (typically synchronously), but when inserted using innerHTML and outerHTML attributes, they do not execute at all.

In this example, two script elements are used. One embeds an external script, and the other includes some data.

<script src="game-engine.js"></script>
<script type="text/x-game-map">
........U.........e
o............A....e
.....A.....AAA....e
.A..AAA...AAAAA...e
</script>

The data in this case might be used by the script to generate the map of a video game. The data doesn't have to be used that way, though; maybe the map data is actually embedded in other parts of the page's markup, and the data block here is just used by the site's search engine to help users who are looking for particular features in their game maps.

The following sample shows how a script element can be used to define a function that is then used by other parts of the document. It also shows how a script element can be used to invoke script while the document is being parsed, in this case to initialize the form's output.

<script>
 function calculate(form) {
   var price = 52000;
   if (form.elements.brakes.checked)
     price += 1000;
   if (form.elements.radio.checked)
     price += 2500;
   if (form.elements.turbo.checked)
     price += 5000;
   if (form.elements.sticker.checked)
     price += 250;
   form.elements.result.value = price;
 }
</script>
<form name="pricecalc" onsubmit="return false">
 <fieldset>
  <legend>Work out the price of your car</legend>
  <p>Base cost: £52000.</p>
  <p>Select additional options:</p>
  <ul>
   <li><label><input type=checkbox name=brakes> Ceramic brakes (£1000)</label></li>
   <li><label><input type=checkbox name=radio> Satellite radio (£2500)</label></li>
   <li><label><input type=checkbox name=turbo> Turbo charger (£5000)</label></li>
   <li><label><input type=checkbox name=sticker> "XZ" sticker (£250)</label></li>
  </ul>
  <p>Total: £<output name=result onformchange="calculate(form)"></output></p>
 </fieldset>
 <script>
  document.forms.pricecalc.dispatchFormChange();
 </script>
</form>

4.3.1.1 Scripting languages

Status: Last call for comments

A user agent is said to support the scripting language if the script block's type is an ASCII case-insensitive match for the MIME type string of a scripting language that the user agent implements.

The following lists some MIME type strings and the languages to which they refer:

"application/ecmascript"
"application/javascript"
"application/x-ecmascript"
"application/x-javascript"
"text/ecmascript"
"text/javascript"
"text/javascript1.0"
"text/javascript1.1"
"text/javascript1.2"
"text/javascript1.3"
"text/javascript1.4"
"text/javascript1.5"
"text/jscript"
"text/livescript"
"text/x-ecmascript"
"text/x-javascript": JavaScript. [ECMA262]
"text/javascript;e4x=1": JavaScript with ECMAScript for XML. [ECMA357]

User agents may support other MIME types and other languages.

4.3.1.2 Restrictions for contents of `script` elements

Status: Last call for comments

The textContent of a script element must match the script production in the following ABNF, the character set for which is Unicode. [ABNF]

script        = data1 *( escape [ script-start data3 ] "-->" data1 ) [ escape ]
escape        = "<!--" data2 *( script-start data3 script-end data2 )

data1         = <any string that doesn't contain a substring that matches not-data1>
not-data1     = "<!--"             

data2         = <any string that doesn't contain a substring that matches not-data2>
not-data2     = script-start / "-->"  

data3         = <any string that doesn't contain a substring that matches not-data3>
not-data3     = script-end / "-->"

script-start  = lt       s c r i p t tag-end
script-end    = lt slash s c r i p t tag-end

lt            =  %x003C ; U+003C LESS-THAN SIGN character (<)
slash         =  %x002F ; U+002F SOLIDUS character (/)

s             =  %x0053 ; U+0053 LATIN CAPITAL LETTER S
s             =/ %x0073 ; U+0073 LATIN SMALL LETTER S
c             =  %x0043 ; U+0043 LATIN CAPITAL LETTER C
c             =/ %x0063 ; U+0063 LATIN SMALL LETTER C
r             =  %x0052 ; U+0052 LATIN CAPITAL LETTER R
r             =/ %x0072 ; U+0072 LATIN SMALL LETTER R
i             =  %x0049 ; U+0049 LATIN CAPITAL LETTER I
i             =/ %x0069 ; U+0069 LATIN SMALL LETTER I
p             =  %x0050 ; U+0050 LATIN CAPITAL LETTER P
p             =/ %x0070 ; U+0070 LATIN SMALL LETTER P
t             =  %x0054 ; U+0054 LATIN CAPITAL LETTER T
t             =/ %x0074 ; U+0074 LATIN SMALL LETTER T

tag-end       =  %x0009 ; U+0009 CHARACTER TABULATION
tag-end       =/ %x000A ; U+000A LINE FEED (LF)
tag-end       =/ %x000C ; U+000C FORM FEED (FF)
tag-end       =/ %x0020 ; U+0020 SPACE
tag-end       =/ %x002F ; U+002F SOLIDUS (/)
tag-end       =/ %x003E ; U+003E GREATER-THAN SIGN (>)

When a script element contains script documentation, there are further restrictions on the contents of the element, as described in the section below.

4.3.1.3 Inline documentation for external scripts

Status: Last call for comments

If a script element's src attribute is specified, then the contents of the script element, if any, must be such that the value of the text IDL attribute, which is derived from the element's contents, matches the documentation production in the following ABNF, the character set for which is Unicode. [ABNF]

documentation = *( *( space / tab / comment ) [ line-comment ] newline )
comment       = slash star *( not-star / star not-slash ) 1*star slash
line-comment  = slash slash *not-newline

; characters
tab           = %x0009 ; U+0009 TAB
newline       = %x000A ; U+000A LINE FEED (LF)
space         = %x0020 ; U+0020 SPACE
star          = %x002A ; U+002A ASTERISK (*)
slash         = %x002F ; U+002F SOLIDUS (/)
not-newline   = %x0000-0009 / %x000B-10FFFF
                ; a Unicode character other than U+000A LINE FEED (LF)
not-star      = %x0000-0029 / %x002B-10FFFF
                ; a Unicode character other than U+002A ASTERISK (*)
not-slash     = %x0000-002E / %x0030-10FFFF
                ; a Unicode character other than U+002F SOLIDUS (/)

This corresponds to putting the contents of the element in JavaScript comments.

This requirement is in addition to the earlier restrictions on the syntax of contents of script elements.

This allows authors to include documentation, such as license information or API information, inside their documents while still referring to external script files. The syntax is constrained so that authors don't accidentally include what looks like valid script while also providing a src attribute.

<script src="cool-effects.js">
 // create new instances using:
 //    var e = new Effect();
 // start the effect using .play, stop using .stop:
 //    e.play();
 //    e.stop();
</script>

4.3.2 The `noscript` element

Status: Last call for comments

Categories: Metadata content.; Flow content.; Phrasing content.
Contexts in which this element may be used:: In a head element of an HTML document, if there are no ancestor noscript elements.; Where phrasing content is expected in HTML documents, if there are no ancestor noscript elements.
Content model:: When scripting is disabled, in a head element: in any order, zero or more link elements, zero or more style elements, and zero or more meta elements.; When scripting is disabled, not in a head element: transparent, but there must be no noscript element descendants.; Otherwise: text that conforms to the requirements given in the prose.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The noscript element represents nothing if scripting is enabled, and represents its children if scripting is disabled. It is used to present different markup to user agents that support scripting and those that don't support scripting, by affecting how the document is parsed.

When used in HTML documents, the allowed content model is as follows:

In a head element, if scripting is disabled for the noscript element

The noscript element must contain only link, style, and meta elements.

In a head element, if scripting is enabled for the noscript element

The noscript element must contain only text, except that invoking the HTML fragment parsing algorithm with the noscript element as the context element and the text contents as the input must result in a list of nodes that consists only of link, style, and meta elements that would be conforming if they were children of the noscript element, and no parse errors.

Outside of head elements, if scripting is disabled for the noscript element

The noscript element's content model is transparent, with the additional restriction that a noscript element must not have a noscript element as an ancestor (that is, noscript can't be nested).

Outside of head elements, if scripting is enabled for the noscript element

The noscript element must contain only text, except that the text must be such that running the following algorithm results in a conforming document with no noscript elements and no script elements, and such that no step in the algorithm causes an HTML parser to flag a parse error:

Remove every script element from the document.
Make a list of every noscript element in the document. For every noscript element in that list, perform the following steps:
1. Let the parent element be the parent element of the noscript element.
2. Take all the children of the parent element that come before the noscript element, and call these elements the before children.
3. Take all the children of the parent element that come after the noscript element, and call these elements the after children.
4. Let s be the concatenation of all the text node children of the noscript element.
5. Set the innerHTML attribute of the parent element to the value of s. (This, as a side-effect, causes the noscript element to be removed from the document.)
6. Insert the before children at the start of the parent element, preserving their original relative order.
7. Insert the after children at the end of the parent element, preserving their original relative order.

All these contortions are required because, for historical reasons, the noscript element is handled differently by the HTML parser based on whether scripting was enabled or not when the parser was invoked.

The noscript element must not be used in XML documents.

The noscript element is only effective in the HTML syntax, it has no effect in the XHTML syntax.

The noscript element has no other requirements. In particular, children of the noscript element are not exempt from form submission, scripting, and so forth, even when scripting is enabled for the element.

In the following example, a noscript element is used to provide fallback for a script.

<form action="calcSquare.php">
 <p>
  <label for=x>Number</label>:
  <input id="x" name="x" type="number">
 </p>
 <script>
  var x = document.getElementById('x');
  var output = document.createElement('p');
  output.textContent = 'Type a number; it will be squared right then!';
  x.form.appendChild(output);
  x.form.onsubmit = function () { return false; }
  x.oninput = function () {
    var v = x.valueAsNumber;
    output.textContent = v + ' squared is ' + v * v;
  };
 </script>
 <noscript>
  <input type=submit value="Calculate Square">
 </noscript>
</form>

When script is disabled, a button appears to do the calculation on the server side. When script is enabled, the value is computed on-the-fly instead.

The noscript element is a blunt instrument. Sometimes, scripts might be enabled, but for some reason the page's script might fail. For this reason, it's generally better to avoid using noscript, and to instead design the script to change the page from being a scriptless page to a scripted page on the fly, as in the next example:

<form action="calcSquare.php">
 <p>
  <label for=x>Number</label>:
  <input id="x" name="x" type="number">
 </p>
 <input id="submit" type=submit value="Calculate Square">
 <script>
  var x = document.getElementById('x');
  var output = document.createElement('p');
  output.textContent = 'Type a number; it will be squared right then!';
  x.form.appendChild(output);
  x.form.onsubmit = function () { return false; }
  x.oninput = function () {
    var v = x.valueAsNumber;
    output.textContent = v + ' squared is ' + v * v;
  };
  var submit = document.getElementById('submit');
  submit.parentNode.removeChild(submit);
 </script>
</form>

The above technique is also useful in XHTML, since noscript is not supported in the XHTML syntax.

4.4 Sections

Status: Last call for comments

4.4.1 The `body` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

As the second element in an html element.

Content model:

Content attributes:

onafterprint

onbeforeprint

onbeforeunload

onblur

onerror

onfocus

onhashchange

onload

onmessage

onoffline

ononline

onpagehide

onpageshow

onpopstate

onredo

onresize

onstorage

onundo

onunload

DOM interface:

interface HTMLBodyElement : HTMLElement {
           attribute Function onafterprint;
           attribute Function onbeforeprint;
           attribute Function onbeforeunload;
           attribute Function onblur;
           attribute Function onerror;
           attribute Function onfocus;
           attribute Function onhashchange;
           attribute Function onload;
           attribute Function onmessage;
           attribute Function onoffline;
           attribute Function ononline;
           attribute Function onpopstate;
           attribute Function onpagehide;
           attribute Function onpageshow;
           attribute Function onredo;
           attribute Function onresize;
           attribute Function onstorage;
           attribute Function onundo;
           attribute Function onunload;
};

The body element represents the main content of the document.

In conforming documents, there is only one body element. The document.body IDL attribute provides scripts with easy access to a document's body element.

Some DOM operations (for example, parts of the drag and drop model) are defined in terms of "the body element". This refers to a particular element in the DOM, as per the definition of the term, and not any arbitrary body element.

The body element exposes as event handler content attributes a number of the event handlers of the Window object. It also mirrors their event handler IDL attributes.

The onblur, onerror, onfocus, and onload event handlers of the Window object, exposed on the body element, shadow the generic event handlers with the same names normally supported by HTML elements.

Thus, for example, a bubbling error event fired on a child of the body element of a Document would first trigger the onerror event handler content attributes of that element, then that of the root html element, and only then would it trigger the onerror event handler content attribute on the body element. This is because the event would bubble from the target, to the body, to the html, to the Document, to the Window, and the event handler on the body is watching the Window not the body. A regular event listener attached to the body using addEventListener(), however, would fire when the event bubbled through the body and not when it reaches the Window object.

This page updates an indicator to show whether or not the user is online:

<!DOCTYPE HTML>
<html>
 <head>
  <title>Online or offline?</title>
  <script>
   function update(online) {
     document.getElementById('status').textContent = 
       online ? 'Online' : 'Offline';
   }
  </script>
 </head>
 <body ononline="update(true)"
       onoffline="update(false)"
       onload="update(navigator.onLine)">
  <p>You are: <span id="status">(Unknown)</span></p>
 </body>
</html>

4.4.2 The `section` element

Status: Last call for comments

Categories: Flow content.; Sectioning content.; formatBlock candidate.
Contexts in which this element may be used:: Where flow content is expected.
Content model:: Flow content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The section element represents a generic document or application section. A section, in this context, is a thematic grouping of content, typically with a heading.

Examples of sections would be chapters, the various tabbed pages in a tabbed dialog box, or the numbered sections of a thesis. A Web site's home page could be split into sections for an introduction, news items, contact information.

Authors are encouraged to use the article element instead of the section element when it would make sense to syndicate the contents of the element.

The section element is not a generic container element. When an element is needed for styling purposes or as a convenience for scripting, authors are encouraged to use the div element instead. A general rule is that the section element is appropriate only if the element's contents would be listed explicitly in the document's outline.

In the following example, we see an article (part of a larger Web page) about apples, containing two short sections.

<article>
 <hgroup>
  <h1>Apples</h1>
  <h2>Tasty, delicious fruit!</h2>
 </hgroup>
 <p>The apple is the pomaceous fruit of the apple tree.</p>
 <section>
  <h1>Red Delicious</h1>
  <p>These bright red apples are the most common found in many
  supermarkets.</p>
 </section>
 <section>
  <h1>Granny Smith</h1>
  <p>These juicy, green apples make a great filling for
  apple pies.</p>
 </section>
</article>

Notice how the use of section means that the author can use h1 elements throughout, without having to worry about whether a particular section is at the top level, the second level, the third level, and so on.

Here is a graduation programme with two sections, one for the list of people graduating, and one for the description of the ceremony.

<!DOCTYPE Html>
<Html
 ><Head
   ><Title
     >Graduation Ceremony Summer 2022</Title
   ></Head
 ><Body
   ><H1
     >Graduation</H1
   ><Section
     ><H1
       >Ceremony</H1
     ><P
       >Opening Procession</P
     ><P
       >Speech by Validactorian</P
     ><P
       >Speech by Class President</P
     ><P
       >Presentation of Diplomas</P
     ><P
       >Closing Speech by Headmaster</P
   ></Section
   ><Section
     ><H1
       >Graduates</H1
     ><Ul
       ><Li
         >Molly Carpenter</Li
       ><Li
         >Anastasia Luccio</Li
       ><Li
         >Ebenezar McCoy</Li
       ><Li
         >Karrin Murphy</Li
       ><Li
         >Thomas Raith</Li
       ><Li
         >Susan Rodriguez</Li
     ></Ul
   ></Section
 ></Body
></Html>

4.4.3 The `nav` element

Status: Last call for comments

Categories: Flow content.; Sectioning content.; formatBlock candidate.
Contexts in which this element may be used:: Where flow content is expected.
Content model:: Flow content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The nav element represents a section of a page that links to other pages or to parts within the page: a section with navigation links.

Not all groups of links on a page need to be in a nav element — only sections that consist of major navigation blocks are appropriate for the nav element. In particular, it is common for footers to have a short list of links to various pages of a site, such as the terms of service, the home page, and a copyright page. The footer element alone is sufficient for such cases, without a nav element.

User agents (such as screen readers) that are targeted at users who can benefit from navigation information being omitted in the initial rendering, or who can benefit from navigation information being immediately available, can use this element as a way to determine what content on the page to initially skip and/or provide on request.

In the following example, the page has several places where links are present, but only one of those places is considered a navigation section.

<body>
 <header>
  <h1>Wake up sheeple!</h1>
  <p><a href="news.html">News</a> -
     <a href="blog.html">Blog</a> -
     <a href="forums.html">Forums</a></p>
  <p>Last Modified: <time>2009-04-01</time></p>
  <nav>
   <h1>Navigation</h1>
   <ul>
    <li><a href="articles.html">Index of all articles</a></li>
    <li><a href="today.html">Things sheeple need to wake up for today</a></li>
    <li><a href="successes.html">Sheeple we have managed to wake</a></li>
   </ul>
  </nav>
 </header>
 <div>
  <article>
   <header>
    <h1>My Day at the Beach</h1>
   </header>
   <div>
    <p>Today I went to the beach and had a lot of fun.</p>
    ...more content...
   </div>
   <footer>
    <p>Posted <time pubdate datetime="2009-10-10T14:36-08:00">Thursday</time>.</p>
   </footer>
  </article>
  ...more blog posts...
 </div>
 <footer>
  <p>Copyright © 2006 The Example Company</p>
  <p><a href="about.html">About</a> -
     <a href="policy.html">Privacy Policy</a> -
     <a href="contact.html">Contact Us</a></p>
 </footer>
</body>

Notice the div elements being used to wrap all the contents of the page other than the header and footer, and all the contents of the blog entry other than its header and footer.

In the following example, there are two nav elements, one for primary navigation around the site, and one for secondary navigation around the page itself.

<body>
 <h1>The Wiki Center Of Exampland</h1>
 <nav>
  <ul>
   <li><a href="/">Home</a></li>
   <li><a href="/events">Current Events</a></li>
   ...more...
  </ul>
 </nav>
 <article>
  <header>
   <h1>Demos in Exampland</h1>
   <p>Written by A. N. Other.</p>
  </header>
  <nav>
   <ul>
    <li><a href="#public">Public demonstrations</a></li>
    <li><a href="#destroy">Demolitions</a></li>
    ...more...
   </ul>
  </nav>
  <div>
   <section id="public">
    <h1>Public demonstrations</h1>
    <p>...more...</p>
   </section>
   <section id="destroy">
    <h1>Demolitions</h1>
    <p>...more...</p>
   </section>
   ...more...
  </div>
  <footer>
   <p><a href="?edit">Edit</a> | <a href="?delete">Delete</a> | <a href="?Rename">Rename</a></p>
  </footer>
 </article>
 <footer>
  <p><small>© copyright 1998 Exampland Emperor</small></p>
 </footer>
</body>

4.4.4 The `article` element

Status: Last call for comments

Categories: Flow content.; Sectioning content.; formatBlock candidate.
Contexts in which this element may be used:: Where flow content is expected.
Content model:: Flow content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The article element represents a component of a page that consists of a self-contained composition in a document, page, application, or site and that is intended to be independently distributable or reusable, e.g. in syndication. This could be a forum post, a magazine or newspaper article, a blog entry, a user-submitted comment, an interactive widget or gadget, or any other independent item of content.

When article elements are nested, the inner article elements represent articles that are in principle related to the contents of the outer article. For instance, a blog entry on a site that accepts user-submitted comments could represent the comments as article elements nested within the article element for the blog entry.

Author information associated with an article element (q.v. the address element) does not apply to nested article elements.

When used specifically with content to be redistributed in syndication, the article element is similar in purpose to the entry element in Atom. [ATOM]

The time element's pubdate attribute can be used to provide the publication date for an article element.

This example shows a blog post using the article element:

<article>
 <header>
  <h1>The Very First Rule of Life</h1>
  <p><time pubdate datetime="2009-10-09T14:28-08:00"></time></p>
 </header>
 <p>If there's a microphone anywhere near you, assume it's hot and
 sending whatever you're saying to the world. Seriously.</p>
 <p>...</p>
 <footer>
  <a href="?comments=1">Show comments...</a>
 </footer>
</article>

Here is that same blog post, but showing some of the comments:

<article>
 <header>
  <h1>The Very First Rule of Life</h1>
  <p><time pubdate datetime="2009-10-09T14:28-08:00"></time></p>
 </header>
 <p>If there's a microphone anywhere near you, assume it's hot and
 sending whatever you're saying to the world. Seriously.</p>
 <p>...</p>
 <section>
  <h1>Comments</h1>
  <article>
   <footer>
    <p>Posted by: George Washington</p>
    <p><time pubdate datetime="2009-10-10T19:10-08:00"></time></p>
   </footer>
   <p>Yeah! Especially when talking about your lobbyist friends!</p>
  </article>
  <article>
   <footer>
    <p>Posted by: George Hammond</p>
    <p><time pubdate datetime="2009-10-10T19:15-08:00"></time></p>
   </footer>
   <p>Hey, you have the same first name as me.</p>
  </article>
 </section>
</article>

Notice the use of footer to give the information each comment (such as who wrote it and when): the footer element can appear at the start of its section when appropriate, such as in this case. (Using header in this case wouldn't be wrong either; it's mostly a matter of authoring preference.)

4.4.5 The `aside` element

Status: Last call for comments. ISSUE-91 (aside) blocks progress to Last Call

Categories: Flow content.; Sectioning content.; formatBlock candidate.
Contexts in which this element may be used:: Where flow content is expected.
Content model:: Flow content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The aside element represents a section of a page that consists of content that is tangentially related to the content around the aside element, and which could be considered separate from that content. Such sections are often represented as sidebars in printed typography.

The element can be used for typographical effects like pull quotes or sidebars, for advertising, for groups of nav elements, and for other content that is considered separate from the main content of the page.

It's not appropriate to use the aside element just for parentheticals, since those are part of the main flow of the document.

The following example shows how an aside is used to mark up background material on Switzerland in a much longer news story on Europe.

<aside>
 <h1>Switzerland</h1>
 <p>Switzerland, a land-locked country in the middle of geographic
 Europe, has not joined the geopolitical European Union, though it is
 a signatory to a number of European treaties.</p>
</aside>

The following example shows how an aside is used to mark up a pull quote in a longer article.

...

<p>He later joined a large company, continuing on the same work.
<q>I love my job. People ask me what I do for fun when I'm not at
work. But I'm paid to do my hobby, so I never know what to
answer. Some people wonder what they would do if they didn't have to
work... but I know what I would do, because I was unemployed for a
year, and I filled that time doing exactly what I do now.</q></p>

<aside>
 <q> People ask me what I do for fun when I'm not at work. But I'm
 paid to do my hobby, so I never know what to answer. </q>
</aside>

<p>Of course his work — or should that be hobby? —
isn't his only passion. He also enjoys other pleasures.</p>

...

The following extract shows how aside can be used for blogrolls and other side content on a blog:

<body>
 <header>
  <h1>My wonderful blog</h1>
  <p>My tagline</p>
 </header>
 <aside>
  <!-- this aside contains two sections that are tangentially related
  to the page, namely, links to other blogs, and links to blog posts
  from this blog -->
  <nav>
   <h1>My blogroll</h1>
   <ul>
    <li><a href="http://blog.example.com/">Example Blog</a>
   </ul>
  </nav>
  <nav>
   <h1>Archives</h1>
   <ol reversed>
    <li><a href="/last-post">My last post</a>
    <li><a href="/first-post">My first post</a>
   </ol>
  </nav>
 </aside>
 <aside>
  <!-- this aside is tangentially related to the page also, it
  contains twitter messages from the blog author -->
  <h1>Twitter Feed</h1>
  <blockquote cite="http://twitter.example.net/t31351234">
   <p>I'm on vacation, writing my blog.</p>
  </blockquote>
  <blockquote cite="http://twitter.example.net/t31219752">
   <p>I'm going to go on vacation soon.</p>
  </blockquote>
 </aside>
 <article>
  <!-- this is a blog post -->
  <h1>My last post</h1>
  <p>This is my last post.</p>
  <footer>
   <p><a href="/last-post" rel=bookmark>Permalink</a>
  </footer>
 </article>
 <article>
  <!-- this is also a blog post -->
  <h1>My first post</h1>
  <p>This is my first post.</p>
  <aside>
   <!-- this aside is about the blog post, since it's inside the
   <article> element; it would be wrong, for instance, to put the
   blogroll here, since the blogroll isn't really related to this post
   specifically, only to the page as a whole -->
   <h1>Posting</h1>
   <p>While I'm thinking about it, I wanted to say something about
   posting. Posting is fun!</p>
  </aside>
  <footer>
   <p><a href="/first-post" rel=bookmark>Permalink</a>
  </footer>
 </article>
 <footer>
  <nav>
   <a href="/archives">Archives</a> —
   <a href="/about">About me</a> —
   <a href="/copyright">Copyright</a>
  </nav>
 </footer>
</body>

4.4.6 The `h1`, `h2`, `h3`, `h4`, `h5`, and `h6` elements

Categories

Heading content.

Contexts in which this element may be used:

As a child of an hgroup element.

Where flow content is expected.

Content model:

Content attributes:

DOM interface:

interface HTMLHeadingElement : HTMLElement {};

These elements represent headings for their sections.

The semantics and meaning of these elements are defined in the section on headings and sections.

These elements have a rank given by the number in their name. The h1 element is said to have the highest rank, the h6 element has the lowest rank, and two elements with the same name have equal rank.

These two snippets are equivalent:

<body>
<h1>Let's call it a draw(ing surface)</h1>
<h2>Diving in</h2>
<h2>Simple shapes</h2>
<h2>Canvas coordinates</h2>
<h3>Canvas coordinates diagram</h3>
<h2>Paths</h2>
</body>

<body>
 <h1>Let's call it a draw(ing surface)</h1>
 <section>
  <h1>Diving in</h1>
 </section>
 <section>
  <h1>Simple shapes</h1>
 </section>
 <section>
  <h1>Canvas coordinates</h1>
  <section>
   <h1>Canvas coordinates diagram</h1>
  </section>
 </section>
 <section>
  <h1>Paths</h1>
 </section>
</body>

4.4.7 The `hgroup` element

Status: Last call for comments

Categories: Flow content.; Heading content.; formatBlock candidate.
Contexts in which this element may be used:: Where flow content is expected.
Content model:: One or more h1, h2, h3, h4, h5, and/or h6 elements.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The hgroup element represents the heading of a section. The element is used to group a set of h1–h6 elements when the heading has multiple levels, such as subheadings, alternative titles, or taglines.

For the purposes of document summaries, outlines, and the like, the text of hgroup elements is defined to be the text of the highest ranked h1–h6 element descendant of the hgroup element, if there are any such elements, and the first such element if there are multiple elements with that rank. If there are no such elements, then the text of the hgroup element is the empty string.

Other elements of heading content in the hgroup element indicate subheadings or subtitles.

The rank of an hgroup element is the rank of the highest-ranked h1–h6 element descendant of the hgroup element, if there are any such elements, or otherwise the same as for an h1 element (the highest rank).

The section on headings and sections defines how hgroup elements are assigned to individual sections.

Here are some examples of valid headings. In each case, the emphasized text represents the text that would be used as the heading in an application extracting heading data and ignoring subheadings.

<hgroup>
 <h1>The reality dysfunction</h1>
 <h2>Space is not the only void</h2>
</hgroup>

<hgroup>
 <h1>Dr. Strangelove</h1>
 <h2>Or: How I Learned to Stop Worrying and Love the Bomb</h2>
</hgroup>

The point of using hgroup in these examples is to mask the h2 element (which acts as a secondary title) from the outline algorithm.

4.4.8 The `header` element

Status: Last call for comments

Categories: Flow content.; formatBlock candidate.
Contexts in which this element may be used:: Where flow content is expected.
Content model:: Flow content, but with no header or footer element descendants.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The header element represents a group of introductory or navigational aids.

A header element is intended to usually contain the section's heading (an h1–h6 element or an hgroup element), but this is not required. The header element can also be used to wrap a section's table of contents, a search form, or any relevant logos.

Here are some sample headers. This first one is for a game:

<header>
 <p>Welcome to...</p>
 <h1>Voidwars!</h1>
</header>

The following snippet shows how the element can be used to mark up a specification's header:

<header>
 <hgroup>
  <h1>Scalable Vector Graphics (SVG) 1.2</h1>
  <h2>W3C Working Draft 27 October 2004</h2>
 </hgroup>
 <dl>
  <dt>This version:</dt>
  <dd><a href="http://www.w3.org/TR/2004/WD-SVG12-20041027/">http://www.w3.org/TR/2004/WD-SVG12-20041027/</a></dd>
  <dt>Previous version:</dt>
  <dd><a href="http://www.w3.org/TR/2004/WD-SVG12-20040510/">http://www.w3.org/TR/2004/WD-SVG12-20040510/</a></dd>
  <dt>Latest version of SVG 1.2:</dt>
  <dd><a href="http://www.w3.org/TR/SVG12/">http://www.w3.org/TR/SVG12/</a></dd>
  <dt>Latest SVG Recommendation:</dt>
  <dd><a href="http://www.w3.org/TR/SVG/">http://www.w3.org/TR/SVG/</a></dd>
  <dt>Editor:</dt>
  <dd>Dean Jackson, W3C, <a href="mailto:dean@w3.org">dean@w3.org</a></dd>
  <dt>Authors:</dt>
  <dd>See <a href="#authors">Author List</a></dd>
 </dl>
 <p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notic ...
</header>

The header element is not sectioning content; it doesn't introduce a new section.

In this example, the page has a page heading given by the h1 element, and two subsections whose headings are given by h2 elements. The content after the header element is still part of the last subsection started in the header element, because the header element doesn't take part in the outline algorithm.

<body>
 <header>
  <h1>Little Green Guys With Guns</h1>
  <nav>
   <ul>
    <li><a href="/games">Games</a>
    <li><a href="/forum">Forum</a>
    <li><a href="/download">Download</a>
   </ul>
  </nav>
  <h2>Important News</h2> <!-- this starts a second subsection -->
  <!-- this is part of the subsection entitled "Important News" -->
  <p>To play today's games you will need to update your client.</p>
  <h2>Games</h2> <!-- this starts a third subsection -->
 </header>
 <p>You have three active games:</p>
 <!-- this is still part of the subsection entitled "Games" -->
 ...

Status: Last call for comments

Categories: Flow content.; formatBlock candidate.
Contexts in which this element may be used:: Where flow content is expected.
Content model:: Flow content, but with no header or footer element descendants.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The footer element represents a footer for its nearest ancestor sectioning content or sectioning root element. A footer typically contains information about its section such as who wrote it, links to related documents, copyright data, and the like.

Contact information for the author or editor of a section belongs in an address element, possibly itself inside a footer.

Footers don't necessarily have to appear at the end of a section, though they usually do.

When the footer element contains entire sections, they represent appendices, indexes, long colophons, verbose license agreements, and other such content.

The footer element is not sectioning content; it doesn't introduce a new section.

When the nearest ancestor sectioning content or sectioning root element is the body element, then it applies to the whole page.

Here is a page with two footers, one at the top and one at the bottom, with the same content:

<body>
 <footer><a href="../">Back to index...</a></footer>
 <hgroup>
  <h1>Lorem ipsum</h1>
  <h2>The ipsum of all lorems</h2>
 </hgroup>
 <p>A dolor sit amet, consectetur adipisicing elit, sed do eiusmod
 tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim
 veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex
 ea commodo consequat. Duis aute irure dolor in reprehenderit in
 voluptate velit esse cillum dolore eu fugiat nulla
 pariatur. Excepteur sint occaecat cupidatat non proident, sunt in
 culpa qui officia deserunt mollit anim id est laborum.</p>
 <footer><a href="../">Back to index...</a></footer>
</body>

Here is an example which shows the footer element being used both for a site-wide footer and for a section footer.

<!DOCTYPE HTML>
<HTML><HEAD>
<TITLE>The Ramblings of a Scientist</TITLE>
<BODY>
<H1>The Ramblings of a Scientist</H1>
<ARTICLE>
 <H1>Episode 15</H1>
 <VIDEO SRC="/fm/015.ogv" CONTROLS PRELOAD>
  <P><A HREF="/fm/015.ogv">Download video</A>.</P>
 </VIDEO>
 <FOOTER> <!-- footer for article -->
  <P>Published <TIME PUBDATE DATETIME="2009-10-21T18:26-07:00"></TIME></P>
 </FOOTER>
</ARTICLE>
<ARTICLE>
 <H1>My Favorite Trains</H1>
 <P>I love my trains. My favorite train of all time is a Köf.</P>
 <P>It is fun to see them pull some coal cars because they look so
 dwarfed in comparison.</P>
 <FOOTER> <!-- footer for article -->
  <P>Published <TIME PUBDATE DATETIME="2009-09-15T14:54-07:00"></TIME></P>
 </FOOTER>
</ARTICLE>
<FOOTER> <!-- site wide footer -->
 <NAV>
  <P><A HREF="/credits.html">Credits</A> —
     <A HREF="/tos.html">Terms of Service</A> —
     <A HREF="/index.html">Blog Index</A></P>
 </NAV>
 <P>Copyright © 2009 Gordon Freeman</P>
</FOOTER>
</BODY>
</HTML>

4.4.10 The `address` element

Status: Last call for comments

Categories: Flow content.; formatBlock candidate.
Contexts in which this element may be used:: Where flow content is expected.
Content model:: Flow content, but with no heading content descendants, no sectioning content descendants, and no header, footer, or address element descendants.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The address element represents the contact information for its nearest article or body element ancestor. If that is the body element, then the contact information applies to the document as a whole.

For example, a page at the W3C Web site related to HTML might include the following contact information:

<ADDRESS>
 <A href="../People/Raggett/">Dave Raggett</A>,
 <A href="../People/Arnaud/">Arnaud Le Hors</A>,
 contact persons for the <A href="Activity">W3C HTML Activity</A>
</ADDRESS>

The address element must not be used to represent arbitrary addresses (e.g. postal addresses), unless those addresses are in fact the relevant contact information. (The p element is the appropriate element for marking up postal addresses in general.)

The address element must not contain information other than contact information.

For example, the following is non-conforming use of the address element:

<ADDRESS>Last Modified: 1999/12/24 23:37:50</ADDRESS>

Typically, the address element would be included along with other information in a footer element.

The contact information for a node node is a collection of address elements defined by the first applicable entry from the following list:

If node is an article element
If node is a body element: The contact information consists of all the address elements that have node as an ancestor and do not have another body or article element ancestor that is a descendant of node.
If node has an ancestor element that is an article element
If node has an ancestor element that is a body element: The contact information of node is the same as the contact information of the nearest article or body element ancestor, whichever is nearest.
If node's Document has a body element: The contact information of node is the same as the contact information the body element of the Document.
Otherwise: There is no contact information for node.

User agents may expose the contact information of a node to the user, or use it for other purposes, such as indexing sections based on the sections' contact information.

4.4.11 Headings and sections

Status: Last call for comments

The h1–h6 elements and the hgroup element are headings.

The first element of heading content in an element of sectioning content represents the heading for that section. Subsequent headings of equal or higher rank start new (implied) sections, headings of lower rank start implied subsections that are part of the previous one. In both cases, the element represents the heading of the implied section.

Sectioning content elements are always considered subsections of their nearest ancestor element of sectioning content, regardless of what implied sections other headings may have created.

Certain elements are said to be sectioning roots, including blockquote and td elements. These elements can have their own outlines, but the sections and headings inside these elements do not contribute to the outlines of their ancestors.

For the following fragment:

<body>
 <h1>Foo</h1>
 <h2>Bar</h2>
 <blockquote>
  <h3>Bla</h3>
 </blockquote>
 <p>Baz</p>
 <h2>Quux</h2>
 <section>
  <h3>Thud</h3>
 </section>
 <p>Grunt</p>
</body>

...the structure would be:

Foo (heading of explicit body section, containing the "Grunt" paragraph)
1. Bar (heading starting implied section, containing a block quote and the "Baz" paragraph)
2. Quux (heading starting implied section)
3. Thud (heading of explicit section section)

Notice how the section ends the earlier implicit section so that a later paragraph ("Grunt") is back at the top level.

Sections may contain headings of any rank, but authors are strongly encouraged to either use only h1 elements, or to use elements of the appropriate rank for the section's nesting level.

Authors are also encouraged to explicitly wrap sections in elements of sectioning content, instead of relying on the implicit sections generated by having multiple headings in one element of sectioning content.

For example, the following is correct:

<body>
 <h4>Apples</h4>
 <p>Apples are fruit.</p>
 <section>
  <h2>Taste</h2>
  <p>They taste lovely.</p>
  <h6>Sweet</h6>
  <p>Red apples are sweeter than green ones.</p>
  <h1>Color</h1>
  <p>Apples come in various colors.</p>
 </section>
</body>

However, the same document would be more clearly expressed as:

<body>
 <h1>Apples</h1>
 <p>Apples are fruit.</p>
 <section>
  <h2>Taste</h2>
  <p>They taste lovely.</p>
  <section>
   <h3>Sweet</h3>
   <p>Red apples are sweeter than green ones.</p>
  </section>
 </section>
 <section>
  <h2>Color</h2>
  <p>Apples come in various colors.</p>
 </section>
</body>

Both of the documents above are semantically identical and would produce the same outline in compliant user agents.

4.4.11.1 Creating an outline

Status: Last call for comments

This section defines an algorithm for creating an outline for a sectioning content element or a sectioning root element. It is defined in terms of a walk over the nodes of a DOM tree, in tree order, with each node being visited when it is entered and when it is exited during the walk.

The outline for a sectioning content element or a sectioning root element consists of a list of one or more potentially nested sections. A section is a container that corresponds to some nodes in the original DOM tree. Each section can have one heading associated with it, and can contain any number of further nested sections. The algorithm for the outline also associates each node in the DOM tree with a particular section and potentially a heading. (The sections in the outline aren't section elements, though some may correspond to such elements — they are merely conceptual sections.)

The following markup fragment:

<body>
 <h1>A</h1>
 <p>B</p>
 <h2>C</h2>
 <p>D</p>
 <h2>E</h2>
 <p>F</p>
</body>

...results in the following outline being created for the body node (and thus the entire document):

Section created for body node.

Associated with heading "A".

Also associated with paragraph "B".

Nested sections:
1. Section implied for first h2 element.
  
  Associated with heading "C".
  
  Also associated with paragraph "D".
  
  No nested sections.
2. Section implied for second h2 element.
  
  Associated with heading "E".
  
  Also associated with paragraph "F".
  
  No nested sections.

The algorithm that must be followed during a walk of a DOM subtree rooted at a sectioning content element or a sectioning root element to determine that element's outline is as follows:

Let current outlinee be null. (It holds the element whose outline is being created.)
Let current section be null. (It holds a pointer to a section, so that elements in the DOM can all be associated with a section.)
Create a stack to hold elements, which is used to handle nesting. Initialize this stack to empty.
As you walk over the DOM in tree order, trigger the first relevant step below for each element as you enter and exit it.
If the top of the stack is an element, and you are exiting that element

The element being exited is a heading content element.

Pop that element from the stack.

If the top of the stack is a heading content element

Do nothing.

When entering a sectioning content element or a sectioning root element

If current outlinee is not null, and the current section has no heading, create an implied heading and let that be the heading for the current section.

If current outlinee is not null, push current outlinee onto the stack.

Let current outlinee be the element that is being entered.

Let current section be a newly created section for the current outlinee element.

Let there be a new outline for the new current outlinee, initialized with just the new current section as the only section in the outline.

When exiting a sectioning content element, if the stack is not empty

Pop the top element from the stack, and let the current outlinee be that element.

Let current section be the last section in the outline of the current outlinee element.

Append the outline of the sectioning content element being exited to the current section. (This does not change which section is the last section in the outline.)

When exiting a sectioning root element, if the stack is not empty
Run these steps:
1. Pop the top element from the stack, and let the current outlinee be that element.
2. Let current section be the last section in the outline of the current outlinee element.
3. Finding the deepest child: If current section has no child sections, stop these steps.
4. Let current section be the last child section of the current current section.
5. Go back to the substep labeled finding the deepest child.
When exiting a sectioning content element or a sectioning root element

The current outlinee is the element being exited.

Let current section be the first section in the outline of the current outlinee element.

Skip to the next step in the overall set of steps. (The walk is over.)

If the current outlinee is null

Do nothing.

When entering a heading content element
If the current section has no heading, let the element being entered be the heading for the current section.

Otherwise, if the element being entered has a rank equal to or greater than the heading of the last section of the outline of the current outlinee, then create a new section and append it to the outline of the current outlinee element, so that this new section is the new last section of that outline. Let current section be that new section. Let the element being entered be the new heading for the current section.

Otherwise, run these substeps:
1. Let candidate section be current section.
2. If the element being entered has a rank lower than the rank of the heading of the candidate section, then create a new section, and append it to candidate section. (This does not change which section is the last section in the outline.) Let current section be this new section. Let the element being entered be the new heading for the current section. Abort these substeps.
3. Let new candidate section be the section that contains candidate section in the outline of current outlinee.
4. Let candidate section be new candidate section.
5. Return to step 2.
Push the element being entered onto the stack. (This causes the algorithm to skip any descendants of the element.)

Recall that h1 has the highest rank, and h6 has the lowest rank.
Otherwise

Do nothing.
In addition, whenever you exit a node, after doing the steps above, if current section is not null, associate the node with the section current section.
If the current outlinee is null, then there was no sectioning content element or sectioning root element in the DOM. There is no outline. Abort these steps.
Associate any nodes that were not associated with a section in the steps above with current outlinee as their section.
Associate all nodes with the heading of the section with which they are associated, if any.
If current outlinee is the body element, then the outline created for that element is the outline of the entire document.

The tree of sections created by the algorithm above, or a proper subset thereof, must be used when generating document outlines, for example when generating tables of contents.

When creating an interactive table of contents, entries should jump the user to the relevant sectioning content element, if the section was created for a real element in the original document, or to the relevant heading content element, if the section in the tree was generated for a heading in the above process.

Selecting the first section of the document therefore always takes the user to the top of the document, regardless of where the first heading in the body is to be found.

The outline depth of a heading content element associated with a section section is the number of sections that are ancestors of section in the outline that section finds itself in when the outlines of its Document's elements are created, plus 1. The outline depth of a heading content element not associated with a section is 1.

User agents should provide default headings for sections that do not have explicit section headings.

Consider the following snippet:

<body>
 <nav>
  <p><a href="/">Home</a></p>
 </nav>
 <p>Hello world.</p>
 <aside>
  <p>My cat is cute.</p>
 </aside>
</body>

Although it contains no headings, this snippet has three sections: a document (the body) with two subsections (a nav and an aside). A user agent could present the outline as follows:

Untitled document
1. Navigation
2. Sidebar

These default headings ("Untitled document", "Navigation", "Sidebar") are not specified by this specification, and might vary with the user's language, the page's language, the user's preferences, the user agent implementor's preferences, etc.

The following JavaScript function shows how the tree walk could be implemented. The root argument is the root of the tree to walk, and the enter and exit arguments are callbacks that are called with the nodes as they are entered and exited. [ECMA262]

function (root, enter, exit) {
  var node = root;
  start: while (node) {
    enter(node);
    if (node.firstChild) {
      node = node.firstChild;
      continue start;
    }
    while (node) {
      exit(node);
      if (node.nextSibling) {
        node = node.nextSibling;
        continue start;
      }
      if (node == root)
        node = null;
      else
        node = node.parentNode;
    }
  }
}

4.5 Grouping content

Status: Last call for comments

4.5.1 The `p` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where flow content is expected.

Content model:

Content attributes:

DOM interface:

interface HTMLParagraphElement : HTMLElement {};

The p element represents a paragraph.

The following examples are conforming HTML fragments:

<p>The little kitten gently seated himself on a piece of
carpet. Later in his life, this would be referred to as the time the
cat sat on the mat.</p>

<fieldset>
 <legend>Personal information</legend>
 <p>
   <label>Name: <input name="n"></label>
   <label><input name="anon" type="checkbox"> Hide from other users</label>
 </p>
 <p><label>Address: <textarea name="a"></textarea></label></p>
</fieldset>

<p>There was once an example from Femley,<br>
Whose markup was of dubious quality.<br>
The validator complained,<br>
So the author was pained,<br>
To move the error from the markup to the rhyming.</p>

The p element should not be used when a more specific element is more appropriate.

The following example is technically correct:

<section>
 <!-- ... -->
 <p>Last modified: 2001-04-23</p>
 <p>Author: fred@example.com</p>
</section>

However, it would be better marked-up as:

<section>
 <!-- ... -->
 <footer>Last modified: 2001-04-23</footer>
 <address>Author: fred@example.com</address>
</section>

Or:

<section>
 <!-- ... -->
 <footer>
  <p>Last modified: 2001-04-23</p>
  <address>Author: fred@example.com</address>
 </footer>
</section>

4.5.2 The `hr` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where flow content is expected.

Content model:

Empty.

Content attributes:

DOM interface:

interface HTMLHRElement : HTMLElement {};

The hr element represents a paragraph-level thematic break, e.g. a scene change in a story, or a transition to another topic within a section of a reference book.

The following extract from Pandora's Star by Peter F. Hamilton shows two paragraphs that precede a scene change and the paragraph that follows it. The scene change, represented in the printed book by a gap containing a solitary centered star between the second and third paragraphs, is here represented using the hr element.

<p>Dudley was ninety-two, in his second life, and fast approaching
time for another rejuvenation. Despite his body having the physical
age of a standard fifty-year-old, the prospect of a long degrading
campaign within academia was one he regarded with dread. For a
supposedly advanced civilization, the Intersolar Commonwearth could be
appallingly backward at times, not to mention cruel.</p>
<p><i>Maybe it won't be that bad</i>, he told himself. The lie was
comforting enough to get him through the rest of the night's
shift.</p>
<hr>
<p>The Carlton AllLander drove Dudley home just after dawn. Like the
astronomer, the vehicle was old and worn, but perfectly capable of
doing its job. It had a cheap diesel engine, common enough on a
semi-frontier world like Gralmond, although its drive array was a
thoroughly modern photoneural processor. With its high suspension and
deep-tread tyres it could plough along the dirt track to the
observatory in all weather and seasons, including the metre-deep snow
of Gralmond's winters.</p>

4.5.3 The `br` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Empty.

Content attributes:

DOM interface:

interface HTMLBRElement : HTMLElement {};

The br element represents a line break.

br elements must be used only for line breaks that are actually part of the content, as in poems or addresses.

The following example is correct usage of the br element:

<p>P. Sherman<br>
42 Wallaby Way<br>
Sydney</p>

br elements must not be used for separating thematic groups in a paragraph.

The following examples are non-conforming, as they abuse the br element:

<p><a ...>34 comments.</a><br>
<a ...>Add a comment.</a></p>

<p><label>Name: <input name="name"></label><br>
<label>Address: <input name="address"></label></p>

Here are alternatives to the above, which are correct:

<p><a ...>34 comments.</a></p>
<p><a ...>Add a comment.</a></p>

<p><label>Name: <input name="name"></label></p>
<p><label>Address: <input name="address"></label></p>

If a paragraph consists of nothing but a single br element, it represents a placeholder blank line (e.g. as in a template). Such blank lines must not be used for presentation purposes.

Any content inside br elements must not be considered part of the surrounding text.

A br element does not separate paragraphs for the purposes of the Unicode bidirectional algorithm. [BIDI]

4.5.4 The `pre` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where flow content is expected.

Content model:

Content attributes:

DOM interface:

interface HTMLPreElement : HTMLElement {};

The pre element represents a block of preformatted text, in which structure is represented by typographic conventions rather than by elements.

In the HTML syntax, a leading newline character immediately following the pre element start tag is stripped.

Some examples of cases where the pre element could be used:

Including an e-mail, with paragraphs indicated by blank lines, lists indicated by lines prefixed with a bullet, and so on.
Including fragments of computer code, with structure indicated according to the conventions of that language.
Displaying ASCII art.

Authors are encouraged to consider how preformatted text will be experienced when the formatting is lost, as will be the case for users of speech synthesizers, braille displays, and the like. For cases like ASCII art, it is likely that an alternative presentation, such as a textual description, would be more universally accessible to the readers of the document.

To represent a block of computer code, the pre element can be used with a code element; to represent a block of computer output the pre element can be used with a samp element. Similarly, the kbd element can be used within a pre element to indicate text that the user is to enter.

In the following snippet, a sample of computer code is presented.

<p>This is the <code>Panel</code> constructor:</p>
<pre><code>function Panel(element, canClose, closeHandler) {
  this.element = element;
  this.canClose = canClose;
  this.closeHandler = function () { if (closeHandler) closeHandler() };
}</code></pre>

In the following snippet, samp and kbd elements are mixed in the contents of a pre element to show a session of Zork I.

<pre><samp>You are in an open field west of a big white house with a boarded
front door.
There is a small mailbox here.

></samp> <kbd>open mailbox</kbd>

<samp>Opening the mailbox reveals:
A leaflet.

></samp></pre>

The following shows a contemporary poem that uses the pre element to preserve its unusual formatting, which forms an intrinsic part of the poem itself.

<pre>                maxling

it is with a          heart
               heavy

that i admit loss of a feline
        so           loved

a friend lost to the
        unknown
                                (night)

~cdr 11dec07</pre>

4.5.5 The `blockquote` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where flow content is expected.

Content model:

Content attributes:

cite

DOM interface:

interface HTMLQuoteElement : HTMLElement {
           attribute DOMString cite;
};

The HTMLQuoteElement interface is also used by the q element.

The blockquote element represents a section that is quoted from another source.

Content inside a blockquote must be quoted from another source, whose address, if it has one, should be cited in the cite attribute.

If the cite attribute is present, it must be a valid URL. To obtain the corresponding citation link, the value of the attribute must be resolved relative to the element. User agents should allow users to follow such citation links.

The cite IDL attribute must reflect the element's cite content attribute.

This next example shows the use of cite alongside blockquote:

<p>His next piece was the aptly named <cite>Sonnet 130</cite>:</p>
<blockquote cite="http://quotes.example.org/s/sonnet130.html">
  <p>My mistress' eyes are nothing like the sun,<br>
  Coral is far more red, than her lips red,<br>
  ...

This example shows how a forum post could use blockquote to show what post a user is replying to. The article element is used for each post, to mark up the threading.

<article>
 <h1><a href="http://bacon.example.com/?blog=109431">Bacon on a crowbar</a></h1>
 <article>
  <header><strong>t3yw</strong> 12 points 1 hour ago</header>
  <p>I bet a narwhal would love that.</p>
  <footer><a href="?pid=29578">permalink</a></footer>
  <article>
   <header><strong>greg</strong> 8 points 1 hour ago</header>
   <blockquote><p>I bet a narwhal would love that.</p></blockquote>
   <p>Dude narwhals don't eat bacon.</p>
   <footer><a href="?pid=29579">permalink</a></footer>
   <article>
    <header><strong>t3yw</strong> 15 points 1 hour ago</header>
    <blockquote>
     <blockquote><p>I bet a narwhal would love that.</p></blockquote>
     <p>Dude narwhals don't eat bacon.</p>
    </blockquote>
    <p>Next thing you'll be saying they don't get capes and wizard
    hats either!</p>
    <footer><a href="?pid=29580">permalink</a></footer>
    <article>
     <article>
      <header><strong>boing</strong> -5 points 1 hour ago</header>
      <p>narwhals are worse than ceiling cat</p>
      <footer><a href="?pid=29581">permalink</a></footer>
     </article>
    </article>
   </article>
  </article>
  <article>
   <header><strong>fred</strong> 1 points 23 minutes ago</header>
   <blockquote><p>I bet a narwhal would love that.</p></blockquote>
   <p>I bet they'd love to peel a banana too.</p>
   <footer><a href="?pid=29582">permalink</a></footer>
  </article>
 </article>
</article>

Examples of how to represent a conversation are shown in a later section; it is not appropriate to use the cite and blockquote elements for this purpose.

4.5.6 The `ol` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where flow content is expected.

Content model:

Zero or more li elements.

Content attributes:

reversed

start

DOM interface:

interface HTMLOListElement : HTMLElement {
           attribute boolean reversed;
           attribute long start;
};

The ol element represents a list of items, where the items have been intentionally ordered, such that changing the order would change the meaning of the document.

The items of the list are the li element child nodes of the ol element, in tree order.

The reversed attribute is a boolean attribute. If present, it indicates that the list is a descending list (..., 3, 2, 1). If the attribute is omitted, the list is an ascending list (1, 2, 3, ...).

The start attribute, if present, must be a valid integer giving the ordinal value of the first list item.

If the start attribute is present, user agents must parse it as an integer, in order to determine the attribute's value. The default value, used if the attribute is missing or if the value cannot be converted to a number according to the referenced algorithm, is 1 if the element has no reversed attribute, and is the number of child li elements otherwise.

The first item in the list has the ordinal value given by the ol element's start attribute, unless that li element has a value attribute with a value that can be successfully parsed, in which case it has the ordinal value given by that value attribute.

Each subsequent item in the list has the ordinal value given by its value attribute, if it has one, or, if it doesn't, the ordinal value of the previous item, plus one if the reversed is absent, or minus one if it is present.

The reversed IDL attribute must reflect the value of the reversed content attribute.

The start IDL attribute must reflect the value of the start content attribute.

The following markup shows a list where the order matters, and where the ol element is therefore appropriate. Compare this list to the equivalent list in the ul section to see an example of the same items using the ul element.

<p>I have lived in the following countries (given in the order of when
I first lived there):</p>
<ol>
 <li>Switzerland
 <li>United Kingdom
 <li>United States
 <li>Norway
</ol>

Note how changing the order of the list changes the meaning of the document. In the following example, changing the relative order of the first two items has changed the birthplace of the author:

<p>I have lived in the following countries (given in the order of when
I first lived there):</p>
<ol>
 <li>United Kingdom
 <li>Switzerland
 <li>United States
 <li>Norway
</ol>

4.5.7 The `ul` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where flow content is expected.

Content model:

Zero or more li elements.

Content attributes:

DOM interface:

interface HTMLUListElement : HTMLElement {};

The ul element represents a list of items, where the order of the items is not important — that is, where changing the order would not materially change the meaning of the document.

The items of the list are the li element child nodes of the ul element.

The following markup shows a list where the order does not matter, and where the ul element is therefore appropriate. Compare this list to the equivalent list in the ol section to see an example of the same items using the ol element.

<p>I have lived in the following countries:</p>
<ul>
 <li>Norway
 <li>Switzerland
 <li>United Kingdom
 <li>United States
</ul>

Note that changing the order of the list does not change the meaning of the document. The items in the snippet above are given in alphabetical order, but in the snippet below they are given in order of the size of their current account balance in 2007, without changing the meaning of the document whatsoever:

<p>I have lived in the following countries:</p>
<ul>
 <li>Switzerland
 <li>Norway
 <li>United Kingdom
 <li>United States
</ul>

4.5.8 The `li` element

Status: Last call for comments

Categories

None.

Contexts in which this element may be used:

Inside ol elements.

Inside ul elements.

Inside menu elements.

Content model:

Content attributes:

If the element is a child of an ol element: value

DOM interface:

interface HTMLLIElement : HTMLElement {
           attribute long value;
};

The li element represents a list item. If its parent element is an ol, ul, or menu element, then the element is an item of the parent element's list, as defined for those elements. Otherwise, the list item has no defined list-related relationship to any other li element.

The value attribute, if present, must be a valid integer giving the ordinal value of the list item.

If the value attribute is present, user agents must parse it as an integer, in order to determine the attribute's value. If the attribute's value cannot be converted to a number, the attribute must be treated as if it was absent. The attribute has no default value.

The value attribute is processed relative to the element's parent ol element (q.v.), if there is one. If there is not, the attribute has no effect.

The value IDL attribute must reflect the value of the value content attribute.

The following example, the top ten movies are listed (in reverse order). Note the way the list is given a title by using a figure element and its figcaption element.

<figure>
 <figcaption>The top 10 movies of all time</figcaption>
 <ol>
  <li value="10"><cite>Josie and the Pussycats</cite>, 2001</li>
  <li value="9"><cite lang="sh">Црна мачка, бели мачор</cite>, 1998</li>
  <li value="8"><cite>A Bug's Life</cite>, 1998</li>
  <li value="7"><cite>Toy Story</cite>, 1995</li>
  <li value="6"><cite>Monsters, Inc</cite>, 2001</li>
  <li value="5"><cite>Cars</cite>, 2006</li>
  <li value="4"><cite>Toy Story 2</cite>, 1999</li>
  <li value="3"><cite>Finding Nemo</cite>, 2003</li>
  <li value="2"><cite>The Incredibles</cite>, 2004</li>
  <li value="1"><cite>Ratatouille</cite>, 2007</li>
 </ol>
</figure>

The markup could also be written as follows, using the reversed attribute on the ol element:

<figure>
 <figcaption>The top 10 movies of all time</figcaption>
 <ol reversed>
  <li><cite>Josie and the Pussycats</cite>, 2001</li>
  <li><cite lang="sh">Црна мачка, бели мачор</cite>, 1998</li>
  <li><cite>A Bug's Life</cite>, 1998</li>
  <li><cite>Toy Story</cite>, 1995</li>
  <li><cite>Monsters, Inc</cite>, 2001</li>
  <li><cite>Cars</cite>, 2006</li>
  <li><cite>Toy Story 2</cite>, 1999</li>
  <li><cite>Finding Nemo</cite>, 2003</li>
  <li><cite>The Incredibles</cite>, 2004</li>
  <li><cite>Ratatouille</cite>, 2007</li>
 </ol>
</figure>

If the li element is the child of a menu element and itself has a child that defines a command, then the li element will match the :enabled and :disabled pseudo-classes in the same way as the first such child element does.

4.5.9 The `dl` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where flow content is expected.

Content model:

Zero or more groups each consisting of one or more dt elements followed by one or more dd elements.

Content attributes:

DOM interface:

interface HTMLDListElement : HTMLElement {};

The dl element represents an association list consisting of zero or more name-value groups (a description list). Each group must consist of one or more names (dt elements) followed by one or more values (dd elements). Within a single dl element, there should not be more than one dt element for each name.

Name-value groups may be terms and definitions, metadata topics and values, or any other groups of name-value data.

The values within a group are alternatives; multiple paragraphs forming part of the same value must all be given within the same dd element.

The order of the list of groups, and of the names and values within each group, may be significant.

If a dl element is empty, it contains no groups.

If a dl element contains non-whitespace text nodes, or elements other than dt and dd, then those elements or text nodes do not form part of any groups in that dl.

If a dl element contains only dt elements, then it consists of one group with names but no values.

If a dl element contains only dd elements, then it consists of one group with values but no names.

If a dl element starts with one or more dd elements, then the first group has no associated name.

If a dl element ends with one or more dt elements, then the last group has no associated value.

When a dl element doesn't match its content model, it is often due to accidentally using dd elements in the place of dt elements and vice versa. Conformance checkers can spot such mistakes and might be able to advise authors how to correctly use the markup.

In the following example, one entry ("Authors") is linked to two values ("John" and "Luke").

<dl>
 <dt> Authors
 <dd> John
 <dd> Luke
 <dt> Editor
 <dd> Frank
</dl>

In the following example, one definition is linked to two terms.

<dl>
 <dt lang="en-US"> <dfn>color</dfn> </dt>
 <dt lang="en-GB"> <dfn>colour</dfn> </dt>
 <dd> A sensation which (in humans) derives from the ability of
 the fine structure of the eye to distinguish three differently
 filtered analyses of a view. </dd>
</dl>

The following example illustrates the use of the dl element to mark up metadata of sorts. At the end of the example, one group has two metadata labels ("Authors" and "Editors") and two values ("Robert Rothman" and "Daniel Jackson").

<dl>
 <dt> Last modified time </dt>
 <dd> 2004-12-23T23:33Z </dd>
 <dt> Recommended update interval </dt>
 <dd> 60s </dd>
 <dt> Authors </dt>
 <dt> Editors </dt>
 <dd> Robert Rothman </dd>
 <dd> Daniel Jackson </dd>
</dl>

The following example shows the dl element used to give a set of instructions. The order of the instructions here is important (in the other examples, the order of the blocks was not important).

<p>Determine the victory points as follows (use the
first matching case):</p>
<dl>
 <dt> If you have exactly five gold coins </dt>
 <dd> You get five victory points </dd>
 <dt> If you have one or more gold coins, and you have one or more silver coins </dt>
 <dd> You get two victory points </dd>
 <dt> If you have one or more silver coins </dt>
 <dd> You get one victory point </dd>
 <dt> Otherwise </dt>
 <dd> You get no victory points </dd>
</dl>

The following snippet shows a dl element being used as a glossary. Note the use of dfn to indicate the word being defined.

<dl>
 <dt><dfn>Apartment</dfn>, n.</dt>
 <dd>An execution context grouping one or more threads with one or
 more COM objects.</dd>
 <dt><dfn>Flat</dfn>, n.</dt>
 <dd>A deflated tire.</dd>
 <dt><dfn>Home</dfn>, n.</dt>
 <dd>The user's login directory.</dd>
</dl>

The dl element is inappropriate for marking up dialogue. Examples of how to mark up dialogue are shown below.

4.5.10 The `dt` element

Status: Last call for comments

Categories: None.
Contexts in which this element may be used:: Before dd or dt elements inside dl elements.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The dt element represents the term, or name, part of a term-description group in a description list (dl element).

The dt element itself, when used in a dl element, does not indicate that its contents are a term being defined, but this can be indicated using the dfn element.

4.5.11 The `dd` element

Status: Last call for comments

Categories: None.
Contexts in which this element may be used:: After dt or dd elements inside dl elements.
Content model:: Flow content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The dd element represents the description, definition, or value, part of a term-description group in a description list (dl element).

A dl can be used to define a vocabulary list, like in a dictionary. In the following example, each entry, given by a dt with a dfn, has several dds, showing the various parts of the definition.

<dl>
 <dt><dfn>happiness</dfn></dt>
 <dd class="pronunciation">/'hæ p. nes/</dd>
 <dd class="part-of-speech"><i><abbr>n.</abbr></i></dd>
 <dd>The state of being happy.</dd>
 <dd>Good fortune; success. <q>Oh <b>happiness</b>! It worked!</q></dd>
 <dt><dfn>rejoice</dfn></dt>
 <dd class="pronunciation">/ri jois'/</dd>
 <dd><i class="part-of-speech"><abbr>v.intr.</abbr></i> To be delighted oneself.</dd>
 <dd><i class="part-of-speech"><abbr>v.tr.</abbr></i> To cause one to be delighted.</dd>
</dl>

4.5.12 The `figure` element

Status: Last call for comments. ISSUE-90 (figure) blocks progress to Last Call

Categories: Flow content.; Sectioning root.
Contexts in which this element may be used:: Where flow content is expected.
Content model:: Either: One figcaption element followed by flow content.; Or: Flow content followed by one figcaption element.; Or: Flow content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The figure element represents some flow content, optionally with a caption, that is self-contained and is typically referenced as a single unit from the main flow of the document.

The element can thus be used to annotate illustrations, diagrams, photos, code listings, etc, that are referred to from the main content of the document, but that could, without affecting the flow of the document, be moved away from that primary content, e.g. to the side of the page, to dedicated pages, or to an appendix.

The first figcaption element child of the element, if any, represents the caption of the figure element's contents. If there is no child figcaption element, then there is no caption.

This example shows the figure element to mark up a code listing.

<p>In <a href="#l4">listing 4</a> we see the primary core interface
API declaration.</p>
<figure id="l4">
 <figcaption>Listing 4. The primary core interface API declaration.</figcaption>
 <pre><code>interface PrimaryCore {
 boolean verifyDataLine();
 void sendData(in sequence&lt;byte> data);
 void initSelfDestruct();
}</code></pre>
</figure>
<p>The API is designed to use UTF-8.</p>

Here we see a figure element to mark up a photo.

<figure>
 <img src="bubbles-work.jpeg"
      alt="Bubbles, sitting in his office chair, works on his
           latest project intently.">
 <figcaption>Bubbles at work</figcaption>
</figure>

In this example, we see an image that is not a figure, as well as an image and a video that are.

<h2>Malinko's comics</h2>

<p>This case centered on some sort of "intellectual property"
infringement related to a comic (see Exhibit A). The suit started
after a trailer ending with these words:

<blockquote>
 <img src="promblem-packed-action.png" alt="ROUGH COPY! Promblem-Packed Action!">
</blockquote>

<p>...was aired. A lawyer, armed with a Bigger Notebook, launched a
preemptive strike using snowballs. A complete copy of the trailer is
included with Exhibit B.

<figure>
 <img src="ex-a.png" alt="Two squiggles on a dirty piece of paper.">
 <figcaption>Exhibit A. The alleged <cite>rough copy</cite> comic.</figcaption>
</figure>

<figure>
 <video src="ex-b.mov"></video>
 <figcaption>Exhibit B. The <cite>Rough Copy</cite> trailer.</figcaption>
</figure>

<p>The case was resolved out of court.

Here, a part of a poem is marked up using figure.

<figure>
 <p>'Twas brillig, and the slithy toves<br>
 Did gyre and gimble in the wabe;<br>
 All mimsy were the borogoves,<br>
 And the mome raths outgrabe.</p>
 <figcaption><cite>Jabberwocky</cite> (first verse). Lewis Carroll, 1832-98</figcaption>
</figure>

In this example, which could be part of a much larger work discussing a castle, the figure has three images in it.

<figure>
 <img src="castle1423.jpeg" title="Etching. Anonymous, ca. 1423."
      alt="The castle has one tower, and a tall wall around it.">
 <img src="castle1858.jpeg" title="Oil-based paint on canvas. Maria Towle, 1858."
      alt="The castle now has two towers and two walls.">
 <img src="castle1999.jpeg" title="Film photograph. Peter Jankle, 1999."
      alt="The castle lies in ruins, the original tower all that remains in one piece.">
 <figcaption>The castle through the ages: 1423, 1858, and 1999 respectively.</figcaption>
</figure>

4.5.13 The `figcaption` element

Categories: None.
Contexts in which this element may be used:: As the first or last child of a figure element.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The figcaption element represents a caption or legend for the rest of the contents of the figcaption element's parent figure element, if any.

4.5.14 The `div` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where flow content is expected.

Content model:

Content attributes:

DOM interface:

interface HTMLDivElement : HTMLElement {};

The div element has no special meaning at all. It represents its children. It can be used with the class, lang, and title attributes to mark up semantics common to a group of consecutive elements.

Authors are strongly encouraged to view the div element as an element of last resort, for when no other element is suitable. Use of the div element instead of more appropriate elements leads to poor accessibility for readers and poor maintainability for authors.

For example, a blog post would be marked up using article, a chapter using section, a page's navigation aids using nav, and a group of form controls using fieldset.

On the other hand, div elements can be useful for stylistic purposes or to wrap multiple paragraphs within a section that are all to be annotated in a similar way. In the following example, we see div elements used as a way to set the language of two paragraphs at once, instead of setting the language on the two paragraph elements separately:

<article lang="en-US">
 <h1>My use of language and my cats</h1>
 <p>My cat's behavior hasn't changed much since her absence, except
 that she plays her new physique to the neighbors regularly, in an
 attempt to get pets.</p>
 <div lang="en-GB">
  <p>My other cat, coloured black and white, is a sweetie. He followed
  us to the pool today, walking down the pavement with us. Yesterday
  he apparently visited our neighbours. I wonder if he recognises that
  their flat is a mirror image of ours.</p>
  <p>Hm, I just noticed that in the last paragraph I used British
  English. But I'm supposed to write in American English. So I
  shouldn't say "pavement" or "flat" or "colour"...</p>
 </div>
 <p>I should say "sidewalk" and "apartment" and "color"!</p>
</article>

4.6 Text-level semantics

Status: Last call for comments

4.6.1 The `a` element

Status: Last call for comments

Categories

When the element only contains phrasing content: phrasing content.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Transparent, but there must be no interactive content descendant.

Content attributes:

href

target

ping

rel

media

hreflang

type

DOM interface:

interface HTMLAnchorElement : HTMLElement {
  stringifier attribute DOMString href;
           attribute DOMString target;
           attribute DOMString ping;
           attribute DOMString rel;
  readonly attribute DOMTokenList relList;
           attribute DOMString media;
           attribute DOMString hreflang;
           attribute DOMString type;

           attribute DOMString text;

  // URL decomposition IDL attributes
           attribute DOMString protocol;
           attribute DOMString host;
           attribute DOMString hostname;
           attribute DOMString port;
           attribute DOMString pathname;
           attribute DOMString search;
           attribute DOMString hash;
};

If the a element has an href attribute, then it represents a hyperlink (a hypertext anchor).

If the a element has no href attribute, then the element represents a placeholder for where a link might otherwise have been placed, if it had been relevant.

The target, ping, rel, media, hreflang, and type attributes must be omitted if the href attribute is not present.

If a site uses a consistent navigation toolbar on every page, then the link that would normally link to the page itself could be marked up using an a element:

<nav>
 <ul>
  <li> <a href="/">Home</a> </li>
  <li> <a href="/news">News</a> </li>
  <li> <a>Examples</a> </li>
  <li> <a href="/legal">Legal</a> </li>
 </ul>
</nav>

The href, target and ping attributes affect what happens when users follow hyperlinks created using the a element. The rel, media, hreflang, and type attributes may be used to indicate to the user the likely nature of the target resource before the user follows the link.

The activation behavior of a elements that represent hyperlinks is to run the following steps:

If the DOMActivate event in question is not trusted (i.e. a click() method call was the reason for the event being dispatched), and the a element's target attribute is such that applying the rules for choosing a browsing context given a browsing context name, using the value of the target attribute as the browsing context name, would result in there not being a chosen browsing context, then raise an INVALID_ACCESS_ERR exception and abort these steps.
If the target of the click event is an img element with an ismap attribute specified, then server-side image map processing must be performed, as follows:
1. If the DOMActivate event was dispatched as the result of a real pointing-device-triggered click event on the img element, then let x be the distance in CSS pixels from the left edge of the image's left border, if it has one, or the left edge of the image otherwise, to the location of the click, and let y be the distance in CSS pixels from the top edge of the image's top border, if it has one, or the top edge of the image otherwise, to the location of the click. Otherwise, let x and y be zero.
2. Let the hyperlink suffix be a U+003F QUESTION MARK character, the value of x expressed as a base-ten integer using ASCII digits, a U+002C COMMA character (,), and the value of y expressed as a base-ten integer using ASCII digits. ASCII digits are the characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9).
Finally, the user agent must follow the hyperlink defined by the a element. If the steps above defined a hyperlink suffix, then take that into account when following the hyperlink.

a . text: Same as textContent.

The IDL attributes href, ping, target, rel, media, hreflang, and type, must reflect the respective content attributes of the same name.

The IDL attribute relList must reflect the rel content attribute.

The text IDL attribute, on getting, must return the same value as the textContent IDL attribute on the element, and on setting, must act as if the textContent IDL attribute on the element had been set to the new value.

The a element also supports the complement of URL decomposition IDL attributes, protocol, host, port, hostname, pathname, search, and hash. These must follow the rules given for URL decomposition IDL attributes, with the input being the result of resolving the element's href attribute relative to the element, if there is such an attribute and resolving it is successful, or the empty string otherwise; and the common setter action being the same as setting the element's href attribute to the new output value.

The a element may be wrapped around entire paragraphs, lists, tables, and so forth, even entire sections, so long as there is no interactive content within (e.g. buttons or other links). This example shows how this can be used to make an entire advertising block into a link:

<aside class="advertising">
 <h1>Advertising</h1>
 <a href="http://ad.example.com/?adid=1929&amp;pubid=1422">
  <section>
   <h1>Mellblomatic 9000!</h1>
   <p>Turn all your widgets into mellbloms!</p>
   <p>Only $9.99 plus shipping and handling.</p>
  </section>
 </a>
 <a href="http://ad.example.com/?adid=375&amp;pubid=1422">
  <section>
   <h1>The Mellblom Browser</h1>
   <p>Web browsing at the speed of light.</p>
   <p>No other browser goes faster!</p>
  </section>
 </a>
</aside>

4.6.2 The `em` element

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The em element represents stress emphasis of its contents.

The level of emphasis that a particular piece of content has is given by its number of ancestor em elements.

The placement of emphasis changes the meaning of the sentence. The element thus forms an integral part of the content. The precise way in which emphasis is used in this way depends on the language.

These examples show how changing the emphasis changes the meaning. First, a general statement of fact, with no emphasis:

<p>Cats are cute animals.</p>

By emphasizing the first word, the statement implies that the kind of animal under discussion is in question (maybe someone is asserting that dogs are cute):

<p><em>Cats</em> are cute animals.</p>

Moving the emphasis to the verb, one highlights that the truth of the entire sentence is in question (maybe someone is saying cats are not cute):

<p>Cats <em>are</em> cute animals.</p>

By moving it to the adjective, the exact nature of the cats is reasserted (maybe someone suggested cats were mean animals):

<p>Cats are <em>cute</em> animals.</p>

Similarly, if someone asserted that cats were vegetables, someone correcting this might emphasize the last word:

<p>Cats are cute <em>animals</em>.</p>

By emphasizing the entire sentence, it becomes clear that the speaker is fighting hard to get the point across. This kind of emphasis also typically affects the punctuation, hence the exclamation mark here.

<p><em>Cats are cute animals!</em></p>

Anger mixed with emphasizing the cuteness could lead to markup such as:

<p><em>Cats are <em>cute</em> animals!</em></p>

The em element isn't a generic "italics" element. Sometimes, text is intended to stand out from the rest of the paragraph, as if it was in a different mood or voice. For this, the i element is more appropriate.

The em element also isn't intended to convey importance; for that purpose, the strong element is more appropriate.

4.6.3 The `strong` element

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The strong element represents strong importance for its contents.

The relative level of importance of a piece of content is given by its number of ancestor strong elements; each strong element increases the importance of its contents.

Changing the importance of a piece of text with the strong element does not change the meaning of the sentence.

Here is an example of a warning notice in a game, with the various parts marked up according to how important they are:

<p><strong>Warning.</strong> This dungeon is dangerous.
<strong>Avoid the ducks.</strong> Take any gold you find.
<strong><strong>Do not take any of the diamonds</strong>,
they are explosive and <strong>will destroy anything within
ten meters.</strong></strong> You have been warned.</p>

4.6.4 The `small` element

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The small element represents side comments such as small print.

Small print typically features disclaimers, caveats, legal restrictions, or copyrights. Small print is also sometimes used for attribution, or for satisfying licensing requirements.

The small element does not "de-emphasize" or lower the importance of text emphasized by the em element or marked as important with the strong element.

The small element should not be used for extended spans of text, such as multiple paragraphs, lists, or sections of text. It is only intended for short runs of text. The text of a page listing terms of use, for instance, would not be a suitable candidate for the small element: in such a case, the text is not a side comment, it is the main content of the page.

In this example the footer contains contact information and a copyright notice.

<footer>
 <address>
  For more details, contact
  <a href="mailto:js@example.com">John Smith</a>.
 </address>
 <p><small>© copyright 2038 Example Corp.</small></p>
</footer>

In this second example, the small element is used for a side comment in an article.

<p>Example Corp today announced record profits for the
second quarter <small>(Full Disclosure: Foo News is a subsidiary of
Example Corp)</small>, leading to speculation about a third quarter
merger with Demo Group.</p>

This is distinct from a sidebar, which might be multiple paragraphs long and is removed from the main flow of text. In the following example, we see a sidebar from the same article. This sidebar also has small print, indicating the source of the information in the sidebar.

<aside>
 <h1>Example Corp</h1>
 <p>This company mostly creates small software and Web
 sites.</p>
 <p>The Example Corp company mission is "To provide entertainment
 and news on a sample basis".</p>
 <p><small>Information obtained from <a
 href="http://example.com/about.html">example.com</a> home
 page.</small></p>
</aside>

In this last example, the small element is marked as being important small print.

<p><strong><small>Continued use of this service will result in a kiss.</small></strong></p>

4.6.5 The `cite` element

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The cite element represents the title of a work (e.g. a book, a paper, an essay, a poem, a score, a song, a script, a film, a TV show, a game, a sculpture, a painting, a theatre production, a play, an opera, a musical, an exhibition, a legal case report, etc). This can be a work that is being quoted or referenced in detail (i.e. a citation), or it can just be a work that is mentioned in passing.

A person's name is not the title of a work — even if people call that person a piece of work — and the element must therefore not be used to mark up people's names. (In some cases, the b element might be appropriate for names; e.g. in a gossip article where the names of famous people are keywords rendered with a different style to draw attention to them. In other cases, if an element is really needed, the span element can be used.)

This next example shows a typical use of the cite element:

<p>My favorite book is <cite>The Reality Dysfunction</cite> by
Peter F. Hamilton. My favorite comic is <cite>Pearls Before
Swine</cite> by Stephan Pastis. My favorite track is <cite>Jive
Samba</cite> by the Cannonball Adderley Sextet.</p>

This is correct usage:

<p>According to the Wikipedia article <cite>HTML</cite>, as it
stood in mid-February 2008, leaving attribute values unquoted is
unsafe. This is obviously an over-simplification.</p>

The following, however, is incorrect usage, as the cite element here is containing far more than the title of the work:

<!-- do not copy this example, it is an example of bad usage! -->
<p>According to <cite>the Wikipedia article on HTML</cite>, as it
stood in mid-February 2008, leaving attribute values unquoted is
unsafe. This is obviously an over-simplification.</p>

The cite element is obviously a key part of any citation in a bibliography, but it is only used to mark the title:

<p><cite>Universal Declaration of Human Rights</cite>, United Nations,
December 1948. Adopted by General Assembly resolution 217 A (III).</p>

A citation is not a quote (for which the q element is appropriate).

This is incorrect usage, because cite is not for quotes:

<p><cite>This is wrong!</cite>, said Ian.</p>

This is also incorrect usage, because a person is not a work:

<p><q>This is still wrong!</q>, said <cite>Ian</cite>.</p>

The correct usage does not use a cite element:

<p><q>This is correct</q>, said Ian.</p>

As mentioned above, the b element might be relevant for marking names as being keywords in certain kinds of documents:

<p>And then <b>Ian</b> said <q>this might be right, in a
gossip column, maybe!</q>.</p>

4.6.6 The `q` element

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Phrasing content.
Content attributes:: Global attributes; cite
DOM interface:: Uses HTMLQuoteElement.

The q element represents some phrasing content quoted from another source.

Quotation punctuation (such as quotation marks) that is quoting the contents of the element must not appear immediately before, after, or inside q elements; they will be inserted into the rendering by the user agent.

Content inside a q element must be quoted from another source, whose address, if it has one, should be cited in the cite attribute. The source may be fictional, as when quoting characters in a novel or screenplay.

The q element must not be used in place of quotation marks that do not represent quotes; for example, it is inappropriate to use the q element for marking up sarcastic statements.

The use of q elements to mark up quotations is entirely optional; using explicit quotation punctuation without q elements is just as correct.

Here is a simple example of the use of the q element:

<p>The man said <q>Things that are impossible just take
longer</q>. I disagreed with him.</p>

Here is an example with both an explicit citation link in the q element, and an explicit citation outside:

<p>The W3C page <cite>About W3C</cite> says the W3C's
mission is <q cite="http://www.w3.org/Consortium/">To lead the
World Wide Web to its full potential by developing protocols and
guidelines that ensure long-term growth for the Web</q>. I
disagree with this mission.</p>

In the following example, the quotation itself contains a quotation:

<p>In <cite>Example One</cite>, he writes <q>The man
said <q>Things that are impossible just take longer</q>. I
disagreed with him</q>. Well, I disagree even more!</p>

In the following example, quotation marks are used instead of the q element:

<p>His best argument was ❝I disagree❞, which
I thought was laughable.</p>

In the following example, there is no quote — the quotation marks are used to name a word. Use of the q element in this case would be inappropriate.

<p>The word "ineffable" could have been used to describe the disaster
resulting from the campaign's mismanagement.</p>

4.6.7 The `dfn` element

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Phrasing content, but there must be no dfn element descendants.
Content attributes:: Global attributes; Also, the title attribute has special semantics on this element.
DOM interface:: Uses HTMLElement.

The dfn element represents the defining instance of a term. The paragraph, description list group, or section that is the nearest ancestor of the dfn element must also contain the definition(s) for the term given by the dfn element.

Defining term: If the dfn element has a title attribute, then the exact value of that attribute is the term being defined. Otherwise, if it contains exactly one element child node and no child text nodes, and that child element is an abbr element with a title attribute, then the exact value of that attribute is the term being defined. Otherwise, it is the exact textContent of the dfn element that gives the term being defined.

If the title attribute of the dfn element is present, then it must contain only the term being defined.

The title attribute of ancestor elements does not affect dfn elements.

An a element that links to a dfn element represents an instance of the term defined by the dfn element.

In the following fragment, the term "GDO" is first defined in the first paragraph, then used in the second.

<p>The <dfn><abbr title="Garage Door Opener">GDO</abbr></dfn>
is a device that allows off-world teams to open the iris.</p>
<!-- ... later in the document: -->
<p>Teal'c activated his <abbr title="Garage Door Opener">GDO</abbr>
and so Hammond ordered the iris to be opened.</p>

With the addition of an a element, the reference can be made explicit:

<p>The <dfn id=gdo><abbr title="Garage Door Opener">GDO</abbr></dfn>
is a device that allows off-world teams to open the iris.</p>
<!-- ... later in the document: -->
<p>Teal'c activated his <a href=#gdo><abbr title="Garage Door Opener">GDO</abbr></a>
and so Hammond ordered the iris to be opened.</p>

4.6.8 The `abbr` element

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Phrasing content.
Content attributes:: Global attributes; Also, the title attribute has special semantics on this element.
DOM interface:: Uses HTMLElement.

The abbr element represents an abbreviation or acronym, optionally with its expansion. The title attribute may be used to provide an expansion of the abbreviation. The attribute, if specified, must contain an expansion of the abbreviation, and nothing else.

The paragraph below contains an abbreviation marked up with the abbr element. This paragraph defines the term "Web Hypertext Application Technology Working Group".

<p>The <dfn id=whatwg><abbr
title="Web Hypertext Application Technology Working Group">WHATWG</abbr></dfn>
is a loose unofficial collaboration of Web browser manufacturers and
interested parties who wish to develop new technologies designed to
allow authors to write and deploy Applications over the World Wide
Web.</p>

An alternative way to write this would be:

<p>The <dfn id=whatwg>Web Hypertext Application Technology
Working Group</dfn> (<abbr
title="Web Hypertext Application Technology Working Group">WHATWG</abbr>)
is a loose unofficial collaboration of Web browser manufacturers and
interested parties who wish to develop new technologies designed to
allow authors to write and deploy Applications over the World Wide
Web.</p>

This paragraph has two abbreviations. Notice how only one is defined; the other, with no expansion associated with it, does not use the abbr element.

<p>The
<abbr title="Web Hypertext Application Technology Working Group">WHATWG</abbr>
started working on HTML5 in 2004.</p>

This paragraph links an abbreviation to its definition.

<p>The <a href="#whatwg"><abbr
title="Web Hypertext Application Technology Working Group">WHATWG</abbr></a>
community does not have much representation from Asia.</p>

This paragraph marks up an abbreviation without giving an expansion, possibly as a hook to apply styles for abbreviations (e.g. smallcaps).

<p>Philip` and Dashiva both denied that they were going to
get the issue counts from past revisions of the specification to
backfill the <abbr>WHATWG</abbr> issue graph.</p>

If an abbreviation is pluralized, the expansion's grammatical number (plural vs singular) must match the grammatical number of the contents of the element.

Here the plural is outside the element, so the expansion is in the singular:

<p>Two <abbr title="Working Group">WG</abbr>s worked on
this specification: the <abbr>WHATWG</abbr> and the
<abbr>HTMLWG</abbr>.</p>

Here the plural is inside the element, so the expansion is in the plural:

<p>Two <abbr title="Working Groups">WGs</abbr> worked on
this specification: the <abbr>WHATWG</abbr> and the
<abbr>HTMLWG</abbr>.</p>

Abbreviations do not have to be marked up using this element. It is expected to be useful in the following cases:

Abbreviations for which the author wants to give expansions, where using the abbr element with a title attribute is an alternative to including the expansion inline (e.g. in parentheses).
Abbreviations that are likely to be unfamiliar to the document's readers, for which authors are encouraged to either mark up the abbreviation using a abbr element with a title attribute or include the expansion inline in the text the first time the abbreviation is used.
Abbreviations whose presence needs to be semantically annotated, e.g. so that they can be identified from a style sheet and given specific styles, for which the abbr element can be used without a title attribute.

Providing an expansion in a title attribute once will not necessarily cause other abbr elements in the same document with the same contents but without a title attribute to behave as if they had the same expansion. Every abbr element is independent.

4.6.9 The `time` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Phrasing content, but there must be no time element descendants.

Content attributes:

datetime

pubdate

DOM interface:

interface HTMLTimeElement : HTMLElement {
           attribute DOMString dateTime;
           attribute boolean pubDate;
  readonly attribute Date valueAsDate;
};

The time element represents either a time on a 24 hour clock, or a precise date in the proleptic Gregorian calendar, optionally with a time and a time-zone offset. [GREGORIAN]

This element is intended as a way to encode modern dates and times in a machine-readable way so that, for example, user agents can offer to add birthday reminders or scheduled events to the user's calendar.

The time element is not intended for encoding times for which a precise date or time cannot be established. For example, it would be inappropriate for encoding times like "one millisecond after the big bang", "the early part of the Jurassic period", or "a winter around 250 BCE".

For dates before the introduction of the Gregorian calendar, authors are encouraged to not use the time element, or else to be very careful about converting dates and times from the period to the Gregorian calendar. This is complicated by the manner in which the Gregorian calendar was phased in, which occurred at different times in different countries, ranging from partway through the 16th century all the way to early in the 20th.

The pubdate attribute is a boolean attribute. If specified, it indicates that the date and time given by the element is the publication date and time of the nearest ancestor article element, or, if the element has no ancestor article element, of the document as a whole. If the element has a pubdate attribute specified, then the element needs a date. For each article element, there must no more than one time element with a pubdate attribute whose nearest ancestor is that article element. Furthermore, for each Document, there must be no more than one time element with a pubdate attribute that does not have an ancestor article element.

The datetime attribute, if present, gives the date or time being specified. Otherwise, the date or time is given by the element's contents.

If the element needs a date, and the datetime attribute is present, then the attribute's value must be a valid date string with optional time.

If the element needs a date, but the datetime attribute is not present, then the element's textContent must be a valid date string in content with optional time.

If the element does not need a date, and the datetime attribute is present, then the attribute's value must be a valid date or time string.

If the element does not need a date, but the datetime attribute is not present, then the element's textContent must be a valid date or time string in content.

The date, if any, must be expressed using the Gregorian calendar.

If the datetime attribute is present, the user agent should convey the attribute's value to the user when rendering the element.

The time element can be used to encode dates, for example in Microformats. The following shows a hypothetical way of encoding an event using a variant on hCalendar that uses the time element:

<div class="vevent">
 <a class="url" href="http://www.web2con.com/">http://www.web2con.com/</a>
  <span class="summary">Web 2.0 Conference</span>:
  <time class="dtstart" datetime="2007-10-05">October 5</time> -
  <time class="dtend" datetime="2007-10-20">19</time>,
  at the <span class="location">Argent Hotel, San Francisco, CA</span>
 </div>

(The end date is encoded as one day after the last date of the event because in the iCalendar format, end dates are exclusive, not inclusive.)

The time element is not necessary for encoding dates or times. In the following snippet, the time is encoded using time, so that it can be restyled (e.g. using XBL2) to match local conventions, while the year is not marked up at all, since marking it up would not be particularly useful.

<p>I usually have a snack at <time>16:00</time>.</p>
<p>I've liked model trains since at least 1983.</p>

Using a styling technology that supports restyling times, the first paragraph from the above snippet could be rendered as follows:

I usually have a snack at 4pm.

Or it could be rendered as follows:

I usually have a snack at 16h00.

The dateTime IDL attribute must reflect the datetime content attribute.

The pubDate IDL attribute must reflect the pubdate content attribute.

User agents, to obtain the date, time, and time-zone offset represented by a time element, must follow these steps:

If the datetime attribute is present, then use the rules to parse a date or time string with the flag in attribute from the value of that attribute, and let the result be result.
Otherwise, use the rules to parse a date or time string with the flag in content from the element's textContent, and let the result be result.
If result is empty (because the parsing failed), then the date is unknown, the time is unknown, and the time-zone offset is unknown.
Otherwise: if result contains a date, then that is the date; if result contains a time, then that is the time; and if result contains a time-zone offset, then the time-zone offset is the element's time-zone offset. (A time-zone offset can only be present if both a date and a time are also present.)

time . valueAsDate: Returns a Date object representing the specified date and time.

The valueAsDate IDL attribute must return either null or a new Date object initialised to the relevant value as defined by the following list:

If the date is known but the time is not: The time corresponding to midnight UTC (i.e. the first second) of the given date.
If the time is known but the date is not: The time corresponding to the given time of 1970-01-01, with the time zone UTC.
If both the date and the time are known: The time corresponding to the date and time, with the given time-zone offset.
If neither the date nor the time are known: The null value.

When a Date object is to be returned, a new one must be constructed.

In the following snippet:

<p>Our first date was <time datetime="2006-09-23">a Saturday</time>.</p>

...the time element's valueAsDate attribute would have the value 1,158,969,600,000ms.

In the following snippet:

<p>Many people get up at <time>08:00</time>.</p>

...the time element's valueAsDate attribute would have the value 28,800,000ms.

In this example, an article's publication date is marked up using time:

<article>
 <h1>Small tasks</h1>
 <footer>Published <time pubdate>2009-08-30</time>.</footer>
 <p>I put a bike bell on his bike.</p>
</article>

Here is another way that could be marked up:

<article>
 <h1>Small tasks</h1>
 <footer>Published <time pubdate datetime="2009-08-30">today</time>.</footer>
 <p>I put a bike bell on his bike.</p>
</article>

Here is the same thing but with the time included. Because the element is empty, it will be replaced in the rendering with a more readable version of the date and time given.

<article>
 <h1>Small tasks</h1>
 <footer>Published <time pubdate datetime="2009-08-30T07:13Z"></time>.</footer>
 <p>I put a bike bell on his bike.</p>
</article>

4.6.10 The `code` element

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The code element represents a fragment of computer code. This could be an XML element name, a filename, a computer program, or any other string that a computer would recognize.

Although there is no formal way to indicate the language of computer code being marked up, authors who wish to mark code elements with the language used, e.g. so that syntax highlighting scripts can use the right rules, may do so by adding a class prefixed with "language-" to the element.

The following example shows how the element can be used in a paragraph to mark up element names and computer code, including punctuation.

<p>The <code>code</code> element represents a fragment of computer
code.</p>

<p>When you call the <code>activate()</code> method on the
<code>robotSnowman</code> object, the eyes glow.</p>

<p>The example below uses the <code>begin</code> keyword to indicate
the start of a statement block. It is paired with an <code>end</code>
keyword, which is followed by the <code>.</code> punctuation character
(full stop) to indicate the end of the program.</p>

The following example shows how a block of code could be marked up using the pre and code elements.

<pre><code class="language-pascal">var i: Integer;
begin
   i := 1;
end.</code></pre>

A class is used in that example to indicate the language used.

See the pre element for more details.

4.6.11 The `var` element

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The var element represents a variable. This could be an actual variable in a mathematical expression or programming context, or it could just be a term used as a placeholder in prose.

In the paragraph below, the letter "n" is being used as a variable in prose:

<p>If there are <var>n</var> pipes leading to the ice
cream factory then I expect at <em>least</em> <var>n</var>
flavors of ice cream to be available for purchase!</p>

For mathematics, in particular for anything beyond the simplest of expressions, MathML is more appropriate. However, the var element can still be used to refer to specific variables that are then mentioned in MathML expressions.

In this example, an equation is shown, with a legend that references the variables in the equation. The expression itself is marked up with MathML, but the variables are mentioned in the figure's legend using var.

<figure>
 <math>
  <mi>a</mi>
  <mo>=</mo>
  <msqrt>
   <msup><mi>b</mi><mn>2</mn></msup>
   <mi>+</mi>
   <msup><mi>c</mi><mn>2</mn></msup>
  </msqrt>
 </math>
 <figcaption>
  Using Pythagoras' theorem to solve for the hypotenuse <var>a</var> of
  a triangle with sides <var>b</var> and <var>c</var>
 </figcaption>
</figure>

4.6.12 The `samp` element

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The samp element represents (sample) output from a program or computing system.

See the pre and kbd elements for more details.

This example shows the samp element being used inline:

<p>The computer said <samp>Too much cheese in tray
two</samp> but I didn't know what that meant.</p>

This second example shows a block of sample output. Nested samp and kbd elements allow for the styling of specific elements of the sample output using a style sheet.

<pre><samp><span class="prompt">jdoe@mowmow:~$</span> <kbd>ssh demo.example.com</kbd>
Last login: Tue Apr 12 09:10:17 2005 from mowmow.example.com on pts/1
Linux demo 2.6.10-grsec+gg3+e+fhs6b+nfs+gr0501+++p3+c4a+gr2b-reslog-v6.189 #1 SMP Tue Feb 1 11:22:36 PST 2005 i686 unknown

<span class="prompt">jdoe@demo:~$</span> <span class="cursor">_</span></samp></pre>

4.6.13 The `kbd` element

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The kbd element represents user input (typically keyboard input, although it may also be used to represent other input, such as voice commands).

When the kbd element is nested inside a samp element, it represents the input as it was echoed by the system.

When the kbd element contains a samp element, it represents input based on system output, for example invoking a menu item.

When the kbd element is nested inside another kbd element, it represents an actual key or other single unit of input as appropriate for the input mechanism.

Here the kbd element is used to indicate keys to press:

<p>To make George eat an apple, press <kbd><kbd>Shift</kbd>+<kbd>F3</kbd></kbd></p>

In this second example, the user is told to pick a particular menu item. The outer kbd element marks up a block of input, with the inner kbd elements representing each individual step of the input, and the samp elements inside them indicating that the steps are input based on something being displayed by the system, in this case menu labels:

<p>To make George eat an apple, select
    <kbd><kbd><samp>File</samp></kbd>|<kbd><samp>Eat Apple...</samp></kbd></kbd>
</p>

Such precision isn't necessary; the following is equally fine:

<p>To make George eat an apple, select <kbd>File | Eat Apple...</kbd></p>

4.6.14 The `sub` and `sup` elements

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which these elements may be used:: Where phrasing content is expected.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Use HTMLElement.

The sup element represents a superscript and the sub element represents a subscript.

These elements must be used only to mark up typographical conventions with specific meanings, not for typographical presentation for presentation's sake. For example, it would be inappropriate for the sub and sup elements to be used in the name of the LaTeX document preparation system. In general, authors should use these elements only if the absence of those elements would change the meaning of the content.

In certain languages, superscripts are part of the typographical conventions for some abbreviations.

<p>The most beautiful women are
<span lang="fr"><abbr>M<sup>lle</sup></abbr> Gwendoline</span> and
<span lang="fr"><abbr>M<sup>me</sup></abbr> Denise</span>.</p>

The sub element can be used inside a var element, for variables that have subscripts.

Here, the sub element is used to represents the subscript that identifies the variable in a family of variables:

<p>The coordinate of the <var>i</var>th point is
(<var>x<sub><var>i</var></sub></var>, <var>y<sub><var>i</var></sub></var>).
For example, the 10th point has coordinate
(<var>x<sub>10</sub></var>, <var>y<sub>10</sub></var>).</p>

Mathematical expressions often use subscripts and superscripts. Authors are encouraged to use MathML for marking up mathematics, but authors may opt to use sub and sup if detailed mathematical markup is not desired. [MATHML]

<var>E</var>=<var>m</var><var>c</var><sup>2</sup>

f(<var>x</var>, <var>n</var>) = log<sub>4</sub><var>x</var><sup><var>n</var></sup>

4.6.15 The `i` element

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The i element represents a span of text in an alternate voice or mood, or otherwise offset from the normal prose, such as a taxonomic designation, a technical term, an idiomatic phrase from another language, a thought, a ship name, or some other prose whose typical typographic presentation is italicized.

Terms in languages different from the main text should be annotated with lang attributes (or, in XML, lang attributes in the XML namespace).

The examples below show uses of the i element:

<p>The <i class="taxonomy">Felis silvestris catus</i> is cute.</p>
<p>The term <i>prose content</i> is defined above.</p>
<p>There is a certain <i lang="fr">je ne sais quoi</i> in the air.</p>

In the following example, a dream sequence is marked up using i elements.

<p>Raymond tried to sleep.</p>
<p><i>The ship sailed away on Thursday</i>, he
dreamt. <i>The ship had many people aboard, including a beautiful
princess called Carey. He watched her, day-in, day-out, hoping she
would notice him, but she never did.</i></p>
<p><i>Finally one night he picked up the courage to speak with
her—</i></p>
<p>Raymond woke with a start as the fire alarm rang out.</p>

Authors are encouraged to use the class attribute on the i element to identify why the element is being used, so that if the style of a particular use (e.g. dream sequences as opposed to taxonomic terms) is to be changed at a later date, the author doesn't have to go through the entire document (or series of related documents) annotating each use. Similarly, authors are encouraged to consider whether other elements might be more applicable than the i element, for instance the em element for marking up stress emphasis, or the dfn element to mark up the defining instance of a term.

Style sheets can be used to format i elements, just like any other element can be restyled. Thus, it is not the case that content in i elements will necessarily be italicized.

4.6.16 The `b` element

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The b element represents a span of text to be stylistically offset from the normal prose without conveying any extra importance, such as key words in a document abstract, product names in a review, or other spans of text whose typical typographic presentation is boldened.

The following example shows a use of the b element to highlight key words without marking them up as important:

<p>The <b>frobonitor</b> and <b>barbinator</b> components are fried.</p>

In the following example, objects in a text adventure are highlighted as being special by use of the b element.

<p>You enter a small room. Your <b>sword</b> glows
brighter. A <b>rat</b> scurries past the corner wall.</p>

Another case where the b element is appropriate is in marking up the lede (or lead) sentence or paragraph. The following example shows how a BBC article about kittens adopting a rabbit as their own could be marked up:

<article>
 <h2>Kittens 'adopted' by pet rabbit</h2>
 <p><b>Six abandoned kittens have found an unexpected new
 mother figure — a pet rabbit.</b></p>
 <p>Veterinary nurse Melanie Humble took the three-week-old
 kittens to her Aberdeen home.</p>
[...]

The b element should be used as a last resort when no other element is more appropriate. In particular, headings should use the h1 to h6 elements, stress emphasis should use the em element, importance should be denoted with the strong element, and text marked or highlighted should use the mark element.

The following would be incorrect usage:

<p><b>WARNING!</b> Do not frob the barbinator!</p>

In the previous example, the correct element to use would have been strong, not b.

Style sheets can be used to format b elements, just like any other element can be restyled. Thus, it is not the case that content in b elements will necessarily be boldened.

4.6.17 The `mark` element

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The mark element represents a run of text in one document marked or highlighted for reference purposes, due to its relevance in another context. When used in a quotation or other block of text referred to from the prose, it indicates a highlight that was not originally present but which has been added to bring the reader's attention to a part of the text that might not have been considered important by the original author when the block was originally written, but which is now under previously unexpected scrutiny. When used in the main prose of a document, it indicates a part of the document that has been highlighted due to its likely relevance to the user's current activity.

This example shows how the mark element can be used to bring attention to a particular part of a quotation:

<p lang="en-US">Consider the following quote:</p>
<blockquote lang="en-GB">
 <p>Look around and you will find, no-one's really
 <mark>colour</mark> blind.</p>
</blockquote>
<p lang="en-US">As we can tell from the <em>spelling</em> of the word,
the person writing this quote is clearly not American.</p>

Another example of the mark element is highlighting parts of a document that are matching some search string. If someone looked at a document, and the server knew that the user was searching for the word "kitten", then the server might return the document with one paragraph modified as follows:

<p>I also have some <mark>kitten</mark>s who are visiting me
these days. They're really cute. I think they like my garden! Maybe I
should adopt a <mark>kitten</mark>.</p>

In the following snippet, a paragraph of text refers to a specific part of a code fragment.

<p>The highlighted part below is where the error lies:</p>
<pre><code>var i: Integer;
begin
   i := <mark>1.1</mark>;
end.</code></pre>

This is another example showing the use of mark to highlight a part of quoted text that was originally not emphasized. In this example, common typographic conventions have led the author to explicitly style mark elements in quotes to render in italics.

<article>
 <style scoped>
  blockquote mark, q mark {
    font: inherit; font-style: italic;
    text-decoration: none;
    background: transparent; color: inherit;
  }
  .bubble em {
    font: inherit; font-size: larger;
    text-decoration: underline;
  }
 </style>
 <h1>She knew</h1>
 <p>Did you notice the subtle joke in the joke on panel 4?</p>
 <blockquote>
  <p class="bubble">I didn't <em>want</em> to believe. <mark>Of course
  on some level I realized it was a known-plaintext attack.</mark> But I
  couldn't admit it until I saw for myself.</p>
 </blockquote>
 <p>(Emphasis mine.) I thought that was great. It's so pedantic, yet it
 explains everything neatly.</p>
</article>

Note, incidentally, the distinction between the em element in this example, which is part of the original text being quoted, and the mark element, which is highlighting a part for comment.

The following example shows the difference between denoting the importance of a span of text (strong) as opposed to denoting the relevance of a span of text (mark). It is an extract from a textbook, where the extract has had the parts relevant to the exam highlighted. The safety warnings, important though they may be, are apparently not relevant to the exam.

<h3>Wormhole Physics Introduction</h3>

<p><mark>A wormhole in normal conditions can be held open for a
maximum of just under 39 minutes.</mark> Conditions that can increase
the time include a powerful energy source coupled to one or both of
the gates connecting the wormhole, and a large gravity well (such as a
black hole).</p>

<p><mark>Momentum is preserved across the wormhole. Electromagnetic
radiation can travel in both directions through a wormhole,
but matter cannot.</mark></p>

<p>When a wormhole is created, a vortex normally forms.
<strong>Warning: The vortex caused by the wormhole opening will
annihilate anything in its path.</strong> Vortexes can be avoided when
using sufficiently advanced dialing technology.</p>

<p><mark>An obstruction in a gate will prevent it from accepting a
wormhole connection.</mark></p>

4.6.18 The `ruby` element

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: One or more groups of: phrasing content followed either by a single rt element, or an rp element, an rt element, and another rp element.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The ruby element allows one or more spans of phrasing content to be marked with ruby annotations. Ruby annotations are short runs of text presented alongside base text, primarily used in East Asian typography as a guide for pronunciation or to include other annotations. In Japanese, this form of typography is also known as furigana.

A ruby element represents the spans of phrasing content it contains, ignoring all the child rt and rp elements and their descendants. Those spans of phrasing content have associated annotations created using the rt element.

In this example, each ideograph in the Japanese text 漢字 is annotated with its reading in hiragana.

...
<ruby>
 漢 <rt> かん </rt>
 字 <rt> じ　 </rt>
</ruby>
...

This might be rendered as:

The two main ideographs, each with its annotation in hiragana rendered in a smaller font above it.

In this example, each ideograph in the traditional Chinese text 漢字 is annotated with its bopomofo reading.

<ruby>
 漢 <rt> ㄏㄢˋ </rt>
 字 <rt> ㄗˋ　 </rt>
</ruby>

This might be rendered as:

The two main ideographs, each with its bopomofo annotation rendered in a smaller font next to it.

In this example, each ideograph in the simplified Chinese text 汉字 is annotated with its pinyin reading.

...
<ruby>
 汉 <rt> hàn </rt>
 字 <rt> zì  </rt>
</ruby>
...

This might be rendered as:

The two main ideographs, each with its pinyin annotation rendered in a smaller font above it.

4.6.19 The `rt` element

Status: Last call for comments

Categories: None.
Contexts in which this element may be used:: As a child of a ruby element.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The rt element marks the ruby text component of a ruby annotation.

An rt element that is a child of a ruby element represents an annotation (given by its children) for the zero or more nodes of phrasing content that immediately precedes it in the ruby element, ignoring rp elements.

An rt element that is not a child of a ruby element represents the same thing as its children.

4.6.20 The `rp` element

Status: Last call for comments

Categories: None.
Contexts in which this element may be used:: As a child of a ruby element, either immediately before or immediately after an rt element.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The rp element can be used to provide parentheses around a ruby text component of a ruby annotation, to be shown by user agents that don't support ruby annotations.

An rp element that is a child of a ruby element represents nothing and its contents must be ignored. An rp element whose parent element is not a ruby element represents its children.

The example above, in which each ideograph in the text 漢字 is annotated with its kanji reading, could be expanded to use rp so that in legacy user agents the readings are in parentheses:

...
<ruby>
 漢 <rp>(</rp><rt>かん</rt><rp>)</rp>
 字 <rp>(</rp><rt>じ</rt><rp>)</rp>
</ruby>
...

In conforming user agents the rendering would be as above, but in user agents that do not support ruby, the rendering would be:

... 漢 (かん) 字 (じ) ...

4.6.21 The `bdo` element

Status: Last call for comments

Categories: Flow content.; Phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Phrasing content.
Content attributes:: Global attributes; Also, the dir global attribute has special semantics on this element.
DOM interface:: Uses HTMLElement.

The bdo element represents explicit text directionality formatting control for its children. It allows authors to override the Unicode bidirectional algorithm by explicitly specifying a direction override. [BIDI]

Authors must specify the dir attribute on this element, with the value ltr to specify a left-to-right override and with the value rtl to specify a right-to-left override.

If the element has the dir attribute set to the exact value ltr, then for the purposes of the bidi algorithm, the user agent must act as if there was a U+202D LEFT-TO-RIGHT OVERRIDE character at the start of the element, and a U+202C POP DIRECTIONAL FORMATTING at the end of the element.

If the element has the dir attribute set to the exact value rtl, then for the purposes of the bidi algorithm, the user agent must act as if there was a U+202E RIGHT-TO-LEFT OVERRIDE character at the start of the element, and a U+202C POP DIRECTIONAL FORMATTING at the end of the element.

The requirements on handling the bdo element for the bidi algorithm may be implemented indirectly through the style layer. For example, an HTML+CSS user agent should implement these requirements by implementing the CSS 'unicode-bidi' property. [CSS]

4.6.22 The `span` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Content attributes:

DOM interface:

interface HTMLSpanElement : HTMLElement {};

The span element doesn't mean anything on its own, but can be useful when used together with other attributes, e.g. class, lang, or dir. It represents its children.

In this example, a code fragment is marked up using span elements and class attributes so that its keywords and identifiers can be color-coded from CSS:

<pre><code class="lang-c"><span class="keyword">for</span> (<span class="ident">j</span> = 0; <span class="ident">j</span> &lt; 256; <span class="ident">j</span>++) {
  <span class="ident">i_t3</span> = (<span class="ident">i_t3</span> & 0x1ffff) | (<span class="ident">j</span> &lt;&lt; 17);
  <span class="ident">i_t6</span> = (((((((<span class="ident">i_t3</span> >> 3) ^ <span class="ident">i_t3</span>) >> 1) ^ <span class="ident">i_t3</span>) >> 8) ^ <span class="ident">i_t3</span>) >> 5) & 0xff;
  <span class="keyword">if</span> (<span class="ident">i_t6</span> == <span class="ident">i_t1</span>)
    <span class="keyword">break</span>;
}</code></pre>

4.6.23 Usage summary

Status: Last call for comments

This section is non-normative.

Element	Purpose	Example
`a`	Hyperlinks	Visit my <a href="drinks.html">drinks</a> page.
`em`	Stress emphasis	I must say I <em>adore</em> lemonade.
`strong`	Importance	This tea is <strong>very hot</strong>.
`small`	Side comments	These grapes are made into wine. <small>Alcohol is addictive.</small>
`cite`	Titles of works	The case <cite>Hugo v. Danielle</cite> is relevant here.
`q`	Quotations	The judge said <q>You can drink water from the fish tank</q> but advised against it.
`dfn`	Defining instance	The term <dfn>organic food</dfn> refers to food produced without synthetic chemicals.
`abbr`	Abbreviations	Organic food in Ireland is certified by the <abbr title="Irish Organic Farmers and Growers Association">IOFGA</abbr>.
`time`	Date and/or time	Published <time>2009-10-21</time>.
`code`	Computer code	The <code>fruitdb</code> program can be used for tracking fruit production.
`var`	Variables	If there are <var>n</var> fruit in the bowl, at least <var>n</var>÷2 will be ripe.
`samp`	Computer output	The computer said <samp>Unknown error -3</samp>.
`kbd`	User input	Hit <kbd>F1</kbd> to continue.
`sub`	Subscripts	Water is H<sub>2</sub>O.
`sup`	Superscripts	The Hydrogen in heavy water is usually <sup>2</sup>H.
`i`	Alternative voice	Lemonade consists primarily of <i>Citrus limon</i>.
`b`	Keywords	Take a <b>lemon</b> and squeeze it with a <b>juicer</b>.
`mark`	Highlight	Elderflower cordial, with one <mark>part</mark> cordial to ten <mark>part</mark>s water, stands a<mark>part</mark> from the rest.
`ruby`, `rt`, `rp`	Ruby annotations	<ruby> OJ <rp>(<rt>Orange Juice<rp>)</ruby>
`bdo`	Text directionality formatting	The proposal is to write English, but in reverse order. "Juice" would become "<bdo dir=rtl>Juice</bdo>"
`span`	Other	In French we call it <span lang="fr">sirop de sureau</span>.

4.7 Edits

Status: Last call for comments

The ins and del elements represent edits to the document.

4.7.1 The `ins` element

Status: Last call for comments

Categories: Flow content.; When the element only contains phrasing content: phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Transparent.
Content attributes:: Global attributes; cite; datetime
DOM interface:: Uses the HTMLModElement interface.

The ins element represents an addition to the document.

The following represents the addition of a single paragraph:

<aside>
 <ins>
  <p> I like fruit. </p>
 </ins>
</aside>

As does this, because everything in the aside element here counts as phrasing content and therefore there is just one paragraph:

<aside>
 <ins>
  Apples are <em>tasty</em>.
 </ins>
 <ins>
  So are pears.
 </ins>
</aside>

ins elements should not cross implied paragraph boundaries.

The following example represents the addition of two paragraphs, the second of which was inserted in two parts. The first ins element in this example thus crosses a paragraph boundary, which is considered poor form.

<aside>
 <!-- don't do this -->
 <ins datetime="2005-03-16T00:00Z">
  <p> I like fruit. </p>
  Apples are <em>tasty</em>.
 </ins>
 <ins datetime="2007-12-19T00:00Z">
  So are pears.
 </ins>
</aside>

Here is a better way of marking this up. It uses more elements, but none of the elements cross implied paragraph boundaries.

<aside>
 <ins datetime="2005-03-16T00:00Z">
  <p> I like fruit. </p>
 </ins>
 <ins datetime="2005-03-16T00:00Z">
  Apples are <em>tasty</em>.
 </ins>
 <ins datetime="2007-12-19T00:00Z">
  So are pears.
 </ins>
</aside>

4.7.2 The `del` element

Status: Last call for comments

Categories: Flow content.; When the element only contains phrasing content: phrasing content.
Contexts in which this element may be used:: Where phrasing content is expected.
Content model:: Transparent.
Content attributes:: Global attributes; cite; datetime
DOM interface:: Uses the HTMLModElement interface.

The del element represents a removal from the document.

del elements should not cross implied paragraph boundaries.

The following shows a "to do" list where items that have been done are crossed-off with the date and time of their completion.

<h1>To Do</h1>
<ul>
 <li>Empty the dishwasher</li>
 <li><del datetime="2009-10-11T01:25-07:00">Watch Walter Lewin's lectures</del></li>
 <li><del datetime="2009-10-10T23:38-07:00">Download more tracks</del></li>
 <li>Buy a printer</li>
</ul>

4.7.3 Attributes common to `ins` and `del` elements

Status: Last call for comments

The cite attribute may be used to specify the address of a document that explains the change. When that document is long, for instance the minutes of a meeting, authors are encouraged to include a fragment identifier pointing to the specific part of that document that discusses the change.

If the cite attribute is present, it must be a valid URL that explains the change. To obtain the corresponding citation link, the value of the attribute must be resolved relative to the element. User agents should allow users to follow such citation links.

The datetime attribute may be used to specify the time and date of the change.

If present, the datetime attribute must be a valid global date and time string value.

User agents must parse the datetime attribute according to the parse a global date and time string algorithm. If that doesn't return a time, then the modification has no associated timestamp (the value is non-conforming; it is not a valid global date and time string). Otherwise, the modification is marked as having been made at the given datetime. User agents should use the associated time-zone offset information to determine which time zone to present the given datetime in.

The ins and del elements must implement the HTMLModElement interface:

interface HTMLModElement : HTMLElement {
           attribute DOMString cite;
           attribute DOMString dateTime;
};

The cite IDL attribute must reflect the element's cite content attribute. The dateTime IDL attribute must reflect the element's datetime content attribute.

4.7.4 Edits and paragraphs

Status: Last call for comments

This section is non-normative.

Since the ins and del elements do not affect paragraphing, it is possible, in some cases where paragraphs are implied (without explicit p elements), for an ins or del element to span both an entire paragraph or other non-phrasing content elements and part of another paragraph. For example:

<section>
 <ins>
  <p>
   This is a paragraph that was inserted.
  </p>
  This is another paragraph whose first sentence was inserted
  at the same time as the paragraph above.
 </ins>
 This is a second sentence, which was there all along.
</section>

By only wrapping some paragraphs in p elements, one can even get the end of one paragraph, a whole second paragraph, and the start of a third paragraph to be covered by the same ins or del element (though this is very confusing, and not considered good practice):

<section>
 This is the first paragraph. <ins>This sentence was
 inserted.
 <p>This second paragraph was inserted.</p>
 This sentence was inserted too.</ins> This is the
 third paragraph in this example.
 <!-- (don't do this) -->
</section>

However, due to the way implied paragraphs are defined, it is not possible to mark up the end of one paragraph and the start of the very next one using the same ins or del element. You instead have to use one (or two) p element(s) and two ins or del elements, as for example:

<section>
 <p>This is the first paragraph. <del>This sentence was
 deleted.</del></p>
 <p><del>This sentence was deleted too.</del> That
 sentence needed a separate &lt;del&gt; element.</p>
</section>

Partly because of the confusion described above, authors are strongly encouraged to always mark up all paragraphs with the p element, instead of having ins or del elements that cross implied paragraphs boundaries.

4.7.5 Edits and lists

Status: Last call for comments

This section is non-normative.

The content models of the ol and ul elements do not allow ins and del elements as children. Lists always represent all their items, including items that would otherwise have been marked as deleted.

To indicate that an item is inserted or deleted, an ins or del element can be wrapped around the contents of the li element. To indicate that an item has been replaced by another, a single li element can have one or more del elements followed by one or more ins elements.

In the following example, a list that started empty had items added and removed from it over time. The bits in the example that have been emphasized show the parts that are the "current" state of the list. The list item numbers don't take into account the edits, though.

<h1>Stop-ship bugs</h1>
<ol>
 <li><ins datetime="2008-02-12T15:20Z">Bug 225:
 Rain detector doesn't work in snow</ins></li>
 <li><del datetime="2008-03-01T20:22Z"><ins datetime="2008-02-14T12:02Z">Bug 228:
 Water buffer overflows in April</ins></del></li>
 <li><ins datetime="2008-02-16T13:50Z">Bug 230:
 Water heater doesn't use renewable fuels</ins></li>
 <li><del datetime="2008-02-20T21:15Z"><ins datetime="2008-02-16T14:25Z">Bug 232:
 Carbon dioxide emissions detected after startup</ins></del></li>
</ol>

In the following example, a list that started with just fruit was replaced by a list with just colors.

<h1>List of <del>fruits</del><ins>colors</ins></h1>
<ul>
 <li><del>Lime</del><ins>Green</ins></li>
 <li><del>Apple</del></li>
 <li>Orange</li>
 <li><del>Pear</del></li>
 <li><ins>Teal</ins></li>
 <li><del>Lemon</del><ins>Yellow</ins></li>
 <li>Olive</li>
 <li><ins>Purple</ins></li>
</ul>

4.8 Embedded content

Status: Last call for comments

4.8.1 The `img` element

Status: Last call for comments. ISSUE-30 (longdesc) and ISSUE-66 (image-analysis) block progress to Last Call

Categories

If the element has a usemap attribute: Interactive content.

Contexts in which this element may be used:

Where embedded content is expected.

Content model:

Empty.

Content attributes:

alt

src

usemap

ismap

width

height

DOM interface:

[NamedConstructor=Image(),
 NamedConstructor=Image(in unsigned long width),
 NamedConstructor=Image(in unsigned long width, in unsigned long height)]
interface HTMLImageElement : HTMLElement {
           attribute DOMString alt;
           attribute DOMString src;
           attribute DOMString useMap;
           attribute boolean isMap;
           attribute unsigned long width;
           attribute unsigned long height;
  readonly attribute unsigned long naturalWidth;
  readonly attribute unsigned long naturalHeight;
  readonly attribute boolean complete;
};

An img element represents an image.

The image given by the src attribute is the embedded content, and the value of the alt attribute is the img element's fallback content.

The src attribute must be present, and must contain a valid URL referencing a non-interactive, optionally animated, image resource that is neither paged nor scripted. If the base URI of the element is the same as the document's address, then the src attribute's value must not be the empty string.

Images can thus be static bitmaps (e.g. PNGs, GIFs, JPEGs), single-page vector documents (single-page PDFs, XML files with an SVG root element), animated bitmaps (APNGs, animated GIFs), animated vector graphics (XML files with an SVG root element that use declarative SMIL animation), and so forth. However, this also precludes SVG files with script, multipage PDF files, interactive MNG files, HTML documents, plain text documents, and so forth.

The requirements on the alt attribute's value are described in the next section.

The img must not be used as a layout tool. In particular, img elements should not be used to display transparent images, as they rarely convey meaning and rarely add anything useful to the document.

Unless the user agent cannot support images, or its support for images has been disabled, or the user agent only fetches elements on demand, or the element's src attribute has a value that is an ignored self-reference, then, when an img is created with a src attribute, and whenever the src attribute is set subsequently, the user agent must resolve the value of that attribute, relative to the element, and if that is successful must then fetch that resource.

The src attribute's value is an ignored self-reference if its value is the empty string, and the base URI of the element is the same as the document's address.

Fetching the image must delay the load event of the element's document until the task that is queued by the networking task source once the resource has been fetched (defined below) has been run.

This, unfortunately, can be used to perform a rudimentary port scan of the user's local network (especially in conjunction with scripting, though scripting isn't actually necessary to carry out such an attack). User agents may implement cross-origin access control policies that mitigate this attack.

If the image is in a supported image type and its dimensions are known, then the image is said to be available (this affects exactly what the element represents, as defined below). This can be true even before the image is completely downloaded, if the user agent supports incremental rendering of images; in such cases, each task that is queued by the networking task source while the image is being fetched must update the presentation of the image appropriately. It can also stop being true, e.g. if the user agent finds, after obtaining the image's dimensions, that the image data is actually fatally corrupted.

If the image was not fetched (e.g. because the UA's image support is disabled, or because the src attribute's value is an ignored self-reference), or if the conditions in the previous paragraph are not met, then the image is not available.

An image might be available in one view but not another. For instance, a Document could be rendered by a screen reader providing a speech synthesis view of the output of a Web browser using the screen media. In this case, the image would be available in the Web browser's screen view, but not available in the screen reader's view.

Whether the image is fetched successfully or not (e.g. whether the response code was a 2xx code or equivalent) must be ignored when determining the image's type and whether it is a valid image.

This allows servers to return images with error responses, and have them displayed.

The user agents should apply the image sniffing rules to determine the type of the image, with the image's associated Content-Type headers giving the official type. If these rules are not applied, then the type of the image must be the type given by the image's associated Content-Type headers.

User agents must not support non-image resources with the img element (e.g. XML files whose root element is an HTML element). User agents must not run executable code (e.g. scripts) embedded in the image resource. User agents must only display the first page of a multipage resource (e.g. a PDF file). User agents must not allow the resource to act in an interactive fashion, but should honor any animation in the resource.

This specification does not specify which image types are to be supported.

The task that is queued by the networking task source once the resource has been fetched, must act as appropriate given the following alternatives:

If the download was successful and the image is available: Queue a task to fire a simple event named load at the img element (this happens after complete starts returning true).
Otherwise (the fetching process failed without a response from the remote server, or completed but the image is not a supported image): Queue a task to fire a simple event named error on the img element.

The task source for these tasks is the DOM manipulation task source.

What an img element represents depends on the src attribute and the alt attribute.

If the src attribute is set and the alt attribute is set to the empty string

The image is either decorative or supplemental to the rest of the content, redundant with some other information in the document.

If the image is available and the user agent is configured to display that image, then the element represents the image specified by the src attribute.

Otherwise, the element represents nothing, and may be omitted completely from the rendering. User agents may provide the user with a notification that an image is present but has been omitted from the rendering.

If the src attribute is set and the alt attribute is set to a value that isn't empty

The image is a key part of the content; the alt attribute gives a textual equivalent or replacement for the image.

If the image is available and the user agent is configured to display that image, then the element represents the image specified by the src attribute.

Otherwise, the element represents the text given by the alt attribute. User agents may provide the user with a notification that an image is present but has been omitted from the rendering.

If the src attribute is set and the alt attribute is not

The image might be a key part of the content, and there is no textual equivalent of the image available.

In a conforming document, the absence of the alt attribute indicates that the image is a key part of the content but that a textual replacement for the image was not available when the image was generated.

If the image is available, the element represents the image specified by the src attribute.

If the image is not available or if the user agent is not configured to display the image, then the user agent should display some sort of indicator that there is an image that is not being rendered, and may, if requested by the user, or if so configured, or when required to provide contextual information in response to navigation, provide caption information for the image, derived as follows:

If the image has a title attribute whose value is not the empty string, then the value of that attribute is the caption information; abort these steps.
If the image is the child of a figure element that has a child figcaption element, then the contents of the first such figcaption element are the caption information; abort these steps.
Run the algorithm to create the outline for the document.
If the img element did not end up associated with a heading in the outline, or if there are any other images that are lacking an alt attribute and that are associated with the same heading in the outline as the img element in question, then there is no caption information; abort these steps.
The caption information is the heading with which the image is associated according to the outline.

If the src attribute is not set and either the alt attribute is set to the empty string or the alt attribute is not set at all

The element represents nothing.

Otherwise

The element represents the text given by the alt attribute.

The alt attribute does not represent advisory information. User agents must not present the contents of the alt attribute in the same way as content of the title attribute.

User agents may always provide the user with the option to display any image, or to prevent any image from being displayed. User agents may also apply heuristics to help the user make use of the image when the user is unable to see it, e.g. due to a visual disability or because they are using a text terminal with no graphics capabilities. Such heuristics could include, for instance, optical character recognition (OCR) of text found within the image.

While user agents are encouraged to repair cases of missing alt attributes, authors must not rely on such behaviour. Requirements for providing text to act as an alternative for images are described in detail below.

The contents of img elements, if any, are ignored for the purposes of rendering.

The usemap attribute, if present, can indicate that the image has an associated image map.

The ismap attribute, when used on an element that is a descendant of an a element with an href attribute, indicates by its presence that the element provides access to a server-side image map. This affects how events are handled on the corresponding a element.

The ismap attribute is a boolean attribute. The attribute must not be specified on an element that does not have an ancestor a element with an href attribute.

The img element supports dimension attributes.

The IDL attributes alt, src, useMap, and isMap each must reflect the respective content attributes of the same name.

image . width [ = value ]

image . height [ = value ]

These attributes return the actual rendered dimensions of the image, or zero if the dimensions are not known.

They can be set, to change the corresponding content attributes.

image . naturalWidth

image . naturalHeight

These attributes return the intrinsic dimensions of the image, or zero if the dimensions are not known.

image . complete

Returns true if the image has been downloaded, decoded, and found to be valid; otherwise, returns false.

image = new Image( [ width [, height ] ] )

Returns a new img element, with the width and height attributes set to the values passed in the relevant arguments, if applicable.

The IDL attributes width and height must return the rendered width and height of the image, in CSS pixels, if the image is being rendered, and is being rendered to a visual medium; or else the intrinsic width and height of the image, in CSS pixels, if the image is available but not being rendered to a visual medium; or else 0, if the image is not available. [CSS]

On setting, they must act as if they reflected the respective content attributes of the same name.

The IDL attributes naturalWidth and naturalHeight must return the intrinsic width and height of the image, in CSS pixels, if the image is available, or else 0. [CSS]

The IDL attribute complete must return true if the user agent has fetched the image specified in the src attribute, and it is in a supported image type (i.e. it was decoded without fatal errors), even if the final task queued by the networking task source for the fetching of the image resource has not yet been processed. Otherwise, the attribute must return false.

The value of complete can thus change while a script is executing.

Three constructors are provided for creating HTMLImageElement objects (in addition to the factory methods from DOM Core such as createElement()): Image(), Image(width), and Image(width, height). When invoked as constructors, these must return a new HTMLImageElement object (a new img element). If the width argument is present, the new object's width content attribute must be set to width. If the height argument is also present, the new object's height content attribute must be set to height. The element's document must be the active document of the browsing context of the Window object on which the interface object of the invoked constructor is found.

A single image can have different appropriate alternative text depending on the context.

In each of the following cases, the same image is used, yet the alt text is different each time. The image is the coat of arms of the Carouge municipality in the canton Geneva in Switzerland.

Here it is used as a supplementary icon:

<p>I lived in <img src="carouge.svg" alt=""> Carouge.</p>

Here it is used as an icon representing the town:

<p>Home town: <img src="carouge.svg" alt="Carouge"></p>

Here it is used as part of a text on the town:

<p>Carouge has a coat of arms.</p>
<p><img src="carouge.svg" alt="The coat of arms depicts a lion, sitting in front of a tree."></p>
<p>It is used as decoration all over the town.</p>

Here it is used as a way to support a similar text where the description is given as well as, instead of as an alternative to, the image:

<p>Carouge has a coat of arms.</p>
<p><img src="carouge.svg" alt=""></p>
<p>The coat of arms depicts a lion, sitting in front of a tree.
It is used as decoration all over the town.</p>

Here it is used as part of a story:

<p>He picked up the folder and a piece of paper fell out.</p>
<p><img src="carouge.svg" alt="Shaped like a shield, the paper had a
red background, a green tree, and a yellow lion with its tongue
hanging out and whose tail was shaped like an S."></p>
<p>He stared at the folder. S! The answer he had been looking for all
this time was simply the letter S! How had he not seen that before? It all
came together now. The phone call where Hector had referred to a lion's tail,
the time Marco had stuck his tongue out...</p>

Here it is not known at the time of publication what the image will be, only that it will be a coat of arms of some kind, and thus no replacement text can be provided, and instead only a brief caption for the image is provided, in the title attribute:

<p>The last user to have uploaded a coat of arms uploaded this one:</p>
<p><img src="last-uploaded-coat-of-arms.cgi" title="User-uploaded coat of arms."></p>

Ideally, the author would find a way to provide real replacement text even in this case, e.g. by asking the previous user. Not providing replacement text makes the document more difficult to use for people who are unable to view images, e.g. blind users, or users or very low-bandwidth connections or who pay by the byte, or users who are forced to use a text-only Web browser.

Here are some more examples showing the same picture used in different contexts, with different appropriate alternate texts each time.

<article>
 <h1>My cats</h1>
 <h2>Fluffy</h2>
 <p>Fluffy is my favorite.</p>
 <img src="fluffy.jpg" alt="She likes playing with a ball of yarn.">
 <p>She's just too cute.</p>
 <h2>Miles</h2>
 <p>My other cat, Miles just eats and sleeps.</p>
</article>

<article>
 <h1>Photography</h1>
 <h2>Shooting moving targets indoors</h2>
 <p>The trick here is to know how to anticipate; to know at what speed and
 what distance the subject will pass by.</p>
 <img src="fluffy.jpg" alt="A cat flying by, chasing a ball of yarn, can be
 photographed quite nicely using this technique.">
 <h2>Nature by night</h2>
 <p>To achieve this, you'll need either an extremely sensitive film, or
 immense flash lights.</p>
</article>

<article>
 <h1>About me</h1>
 <h2>My pets</h2>
 <p>I've got a cat named Fluffy and a dog named Miles.</p>
 <img src="fluffy.jpg" alt="Fluffy, my cat, tends to keep itself busy.">
 <p>My dog Miles and I like go on long walks together.</p>
 <h2>music</h2>
 <p>After our walks, having emptied my mind, I like listening to Bach.</p>
</article>

<article>
 <h1>Fluffy and the Yarn</h1>
 <p>Fluffy was a cat who liked to play with yarn. He also liked to jump.</p>
 <aside><img src="fluffy.jpg" alt="" title="Fluffy"></aside>
 <p>He would play in the morning, he would play in the evening.</p>
</article>

4.8.1.1 Requirements for providing text to act as an alternative for images

Status: Last call for comments. ISSUE-31 (missing-alt) blocks progress to Last Call

The requirements for the alt attribute depend on what the image is intended to represent, as described in the following sections.

4.8.1.1.1 A link or button containing nothing but the image

Status: Last call for comments

When an a element that is a hyperlink, or a button element, has no textual content but contains one or more images, the alt attributes must contain text that together convey the purpose of the link or button.

In this example, a user is asked to pick his preferred color from a list of three. Each color is given by an image, but for users who have configured their user agent not to display images, the color names are used instead:

<h1>Pick your color</h1>
<ul>
 <li><a href="green.html"><img src="green.jpeg" alt="Green"></a></li>
 <li><a href="blue.html"><img src="blue.jpeg" alt="Blue"></a></li>
 <li><a href="red.html"><img src="red.jpeg" alt="Red"></a></li>
</ul>

In this example, each button has a set of images to indicate the kind of color output desired by the user. The first image is used in each case to give the alternative text.

<button name="rgb"><img src="red" alt="RGB"><img src="green" alt=""><img src="blue" alt=""></button>
<button name="cmyk"><img src="cyan" alt="CMYK"><img src="magenta" alt=""><img src="yellow" alt=""><img src="black" alt=""></button>

Since each image represents one part of the text, it could also be written like this:

<button name="rgb"><img src="red" alt="R"><img src="green" alt="G"><img src="blue" alt="B"></button>
<button name="cmyk"><img src="cyan" alt="C"><img src="magenta" alt="M"><img src="yellow" alt="Y"><img src="black" alt="K"></button>

However, with other alternative text, this might not work, and putting all the alternative text into one image in each case might make more sense:

<button name="rgb"><img src="red" alt="sRGB profile"><img src="green" alt=""><img src="blue" alt=""></button>
<button name="cmyk"><img src="cyan" alt="CMYK profile"><img src="magenta" alt=""><img src="yellow" alt=""><img src="black" alt=""></button>

4.8.1.1.2 A phrase or paragraph with an alternative graphical representation: charts, diagrams, graphs, maps, illustrations

Sometimes something can be more clearly stated in graphical form, for example as a flowchart, a diagram, a graph, or a simple map showing directions. In such cases, an image can be given using the img element, but the lesser textual version must still be given, so that users who are unable to view the image (e.g. because they have a very slow connection, or because they are using a text-only browser, or because they are listening to the page being read out by a hands-free automobile voice Web browser, or simply because they are blind) are still able to understand the message being conveyed.

The text must be given in the alt attribute, and must convey the same message as the image specified in the src attribute.

It is important to realize that the alternative text is a replacement for the image, not a description of the image.

In the following example we have a flowchart in image form, with text in the alt attribute rephrasing the flowchart in prose form:

<p>In the common case, the data handled by the tokenization stage
comes from the network, but it can also come from script.</p>
<p><img src="http://dev.w3.org/html5/spec/images/parsing-model-overview.png" alt="The network
passes data to the Tokenizer stage, which passes data to the Tree
Construction stage. From there, data goes to both the DOM and to
Script Execution. Script Execution is linked to the DOM, and, using
document.write(), passes data to the Tokenizer."></p>

Here's another example, showing a good solution and a bad solution to the problem of including an image in a description.

First, here's the good solution. This sample shows how the alternative text should just be what you would have put in the prose if the image had never existed.

<!-- This is the correct way to do things. -->
<p>
 You are standing in an open field west of a house.
 <img src="house.jpeg" alt="The house is white, with a boarded front door.">
 There is a small mailbox here.
</p>

Second, here's the bad solution. In this incorrect way of doing things, the alternative text is simply a description of the image, instead of a textual replacement for the image. It's bad because when the image isn't shown, the text doesn't flow as well as in the first example.

<!-- This is the wrong way to do things. -->
<p>
 You are standing in an open field west of a house.
 <img src="house.jpeg" alt="A white house, with a boarded front door.">
 There is a small mailbox here.
</p>

Text such as "Photo of white house with boarded door" would be equally bad alternative text (though it could be suitable for the title attribute or in the figcaption element of a figure with this image).

4.8.1.1.3 A short phrase or label with an alternative graphical representation: icons, logos

A document can contain information in iconic form. The icon is intended to help users of visual browsers to recognize features at a glance.

In some cases, the icon is supplemental to a text label conveying the same meaning. In those cases, the alt attribute must be present but must be empty.

Here the icons are next to text that conveys the same meaning, so they have an empty alt attribute:

<nav>
 <p><a href="/help/"><img src="/icons/help.png" alt=""> Help</a></p>
 <p><a href="/configure/"><img src="/icons/configuration.png" alt="">
 Configuration Tools</a></p>
</nav>

In other cases, the icon has no text next to it describing what it means; the icon is supposed to be self-explanatory. In those cases, an equivalent textual label must be given in the alt attribute.

Here, posts on a news site are labeled with an icon indicating their topic.

<body>
 <article>
  <header>
   <h1>Ratatouille wins <i>Best Movie of the Year</i> award</h1>
   <p><img src="movies.png" alt="Movies"></p>
  </header>
  <p>Pixar has won yet another <i>Best Movie of the Year</i> award,
  making this its 8th win in the last 12 years.</p>
 </article>
 <article>
  <header>
   <h1>Latest TWiT episode is online</h1>
   <p><img src="podcasts.png" alt="Podcasts"></p>
  </header>
  <p>The latest TWiT episode has been posted, in which we hear
  several tech news stories as well as learning much more about the
  iPhone. This week, the panelists compare how reflective their
  iPhones' Apple logos are.</p>
 </article>
</body>

Many pages include logos, insignia, flags, or emblems, which stand for a particular entity such as a company, organization, project, band, software package, country, or some such.

If the logo is being used to represent the entity, e.g. as a page heading, the alt attribute must contain the name of the entity being represented by the logo. The alt attribute must not contain text like the word "logo", as it is not the fact that it is a logo that is being conveyed, it's the entity itself.

If the logo is being used next to the name of the entity that it represents, then the logo is supplemental, and its alt attribute must instead be empty.

If the logo is merely used as decorative material (as branding, or, for example, as a side image in an article that mentions the entity to which the logo belongs), then the entry below on purely decorative images applies. If the logo is actually being discussed, then it is being used as a phrase or paragraph (the description of the logo) with an alternative graphical representation (the logo itself), and the first entry above applies.

In the following snippets, all four of the above cases are present. First, we see a logo used to represent a company:

<h1><img src="XYZ.gif" alt="The XYZ company"></h1>

Next, we see a paragraph which uses a logo right next to the company name, and so doesn't have any alternative text:

<article>
 <h2>News</h2>
 <p>We have recently been looking at buying the <img src="alpha.gif"
 alt=""> ΑΒΓ company, a small Greek company
 specializing in our type of product.</p>

In this third snippet, we have a logo being used in an aside, as part of the larger article discussing the acquisition:

 <aside><p><img src="alpha-large.gif" alt=""></p></aside>
 <p>The ΑΒΓ company has had a good quarter, and our
 pie chart studies of their accounts suggest a much bigger blue slice
 than its green and orange slices, which is always a good sign.</p>
</article>

Finally, we have an opinion piece talking about a logo, and the logo is therefore described in detail in the alternative text.

<p>Consider for a moment their logo:</p>

<p><img src="/images/logo" alt="It consists of a green circle with a
green question mark centered inside it."></p>

<p>How unoriginal can you get? I mean, oooooh, a question mark, how
<em>revolutionary</em>, how utterly <em>ground-breaking</em>, I'm
sure everyone will rush to adopt those specifications now! They could
at least have tried for some sort of, I don't know, sequence of
rounded squares with varying shades of green and bold white outlines,
at least that would look good on the cover of a blue book.</p>

This example shows how the alternative text should be written such that if the image isn't available, and the text is used instead, the text flows seamlessly into the surrounding text, as if the image had never been there in the first place.

4.8.1.1.4 Text that has been rendered to a graphic for typographical effect

Status: Last call for comments

Sometimes, an image just consists of text, and the purpose of the image is not to highlight the actual typographic effects used to render the text, but just to convey the text itself.

In such cases, the alt attribute must be present but must consist of the same text as written in the image itself.

Consider a graphic containing the text "Earth Day", but with the letters all decorated with flowers and plants. If the text is merely being used as a heading, to spice up the page for graphical users, then the correct alternative text is just the same text "Earth Day", and no mention need be made of the decorations:

<h1><img src="earthdayheading.png" alt="Earth Day"></h1>

4.8.1.1.5 A graphical representation of some of the surrounding text

Status: Last call for comments

In many cases, the image is actually just supplementary, and its presence merely reinforces the surrounding text. In these cases, the alt attribute must be present but its value must be the empty string.

In general, an image falls into this category if removing the image doesn't make the page any less useful, but including the image makes it a lot easier for users of visual browsers to understand the concept.

A flowchart that repeats the previous paragraph in graphical form:

<p>The network passes data to the Tokenizer stage, which
passes data to the Tree Construction stage. From there, data goes
to both the DOM and to Script Execution. Script Execution is
linked to the DOM, and, using document.write(), passes data to
the Tokenizer.</p>
<p><img src="http://dev.w3.org/html5/spec/images/parsing-model-overview.png" alt=""></p>

In these cases, it would be wrong to include alternative text that consists of just a caption. If a caption is to be included, then either the title attribute can be used, or the figure and figcaption elements can be used. In the latter case, the image would in fact be a phrase or paragraph with an alternative graphical representation, and would thus require alternative text.

<!-- Using the title="" attribute -->
<p>The network passes data to the Tokenizer stage, which
passes data to the Tree Construction stage. From there, data goes
to both the DOM and to Script Execution. Script Execution is
linked to the DOM, and, using document.write(), passes data to
the Tokenizer.</p>
<p><img src="http://dev.w3.org/html5/spec/images/parsing-model-overview.png" alt=""
        title="Flowchart representation of the parsing model."></p>

<!-- Using <figure> and <figcaption> -->
<p>The network passes data to the Tokenizer stage, which
passes data to the Tree Construction stage. From there, data goes
to both the DOM and to Script Execution. Script Execution is
linked to the DOM, and, using document.write(), passes data to
the Tokenizer.</p>
<figure>
 <img src="http://dev.w3.org/html5/spec/images/parsing-model-overview.png" alt="The Network leads
 to the Tokenizer, which leads to the Tree Construction. The Tree
 Construction leads to two items. The first is Script Execution, which
 leads via document.write() back to the Tokenizer. The second item
 from which Tree Construction leads is the DOM. The DOM is related to
 the Script Execution.">
 <figcaption>Flowchart representation of the parsing model.</figcaption>
</figure>

<!-- This is WRONG. Do not do this. Instead, do what the above examples do. -->
<p>The network passes data to the Tokenizer stage, which
passes data to the Tree Construction stage. From there, data goes
to both the DOM and to Script Execution. Script Execution is
linked to the DOM, and, using document.write(), passes data to
the Tokenizer.</p>
<p><img src="http://dev.w3.org/html5/spec/images/parsing-model-overview.png"
        alt="Flowchart representation of the parsing model."></p>
<!-- Never put the image's caption in the alt="" attribute! -->

A graph that repeats the previous paragraph in graphical form:

<p>According to a study covering several billion pages,
about 62% of documents on the Web in 2007 triggered the Quirks
rendering mode of Web browsers, about 30% triggered the Almost
Standards mode, and about 9% triggered the Standards mode.</p>
<p><img src="rendering-mode-pie-chart.png" alt=""></p>

4.8.1.1.6 A purely decorative image that doesn't add any information

In general, if an image is decorative but isn't especially page-specific, for example an image that forms part of a site-wide design scheme, the image should be specified in the site's CSS, not in the markup of the document.

However, a decorative image that isn't discussed by the surrounding text but still has some relevance can be included in a page using the img element. Such images are decorative, but still form part of the content. In these cases, the alt attribute must be present but its value must be the empty string.

Examples where the image is purely decorative despite being relevant would include things like a photo of the Black Rock City landscape in a blog post about an event at Burning Man, or an image of a painting inspired by a poem, on a page reciting that poem. The following snippet shows an example of the latter case (only the first verse is included in this snippet):

<h1>The Lady of Shalott</h1>
<p><img src="shalott.jpeg" alt=""></p>
<p>On either side the river lie<br>
Long fields of barley and of rye,<br>
That clothe the wold and meet the sky;<br>
And through the field the road run by<br>
To many-tower'd Camelot;<br>
And up and down the people go,<br>
Gazing where the lilies blow<br>
Round an island there below,<br>
The island of Shalott.</p>

4.8.1.1.7 A group of images that form a single larger picture with no links

Status: Last call for comments

When a picture has been sliced into smaller image files that are then displayed together to form the complete picture again, one of the images must have its alt attribute set as per the relevant rules that would be appropriate for the picture as a whole, and then all the remaining images must have their alt attribute set to the empty string.

In the following example, a picture representing a company logo for XYZ Corp has been split into two pieces, the first containing the letters "XYZ" and the second with the word "Corp". The alternative text ("XYZ Corp") is all in the first image.

<h1><img src="logo1.png" alt="XYZ Corp"><img src="logo2.png" alt=""></h1>

In the following example, a rating is shown as three filled stars and two empty stars. While the alternative text could have been "★★★☆☆", the author has instead decided to more helpfully give the rating in the form "3 out of 5". That is the alternative text of the first image, and the rest have blank alternative text.

<p>Rating: <meter max=5 value=3><img src="1" alt="3 out of 5"
  ><img src="1" alt=""><img src="1" alt=""><img src="0" alt=""
  ><img src="0" alt=""></meter></p>

4.8.1.1.8 A group of images that form a single larger picture with links

Status: Last call for comments

Generally, image maps should be used instead of slicing an image for links.

However, if an image is indeed sliced and any of the components of the sliced picture are the sole contents of links, then one image per link must have alternative text in its alt attribute representing the purpose of the link.

In the following example, a picture representing the flying spaghetti monster emblem, with each of the left noodly appendages and the right noodly appendages in different images, so that the user can pick the left side or the right side in an adventure.

<h1>The Church</h1>
<p>You come across a flying spaghetti monster. Which side of His
Noodliness do you wish to reach out for?</p>
<p><a href="?go=left" ><img src="fsm-left.png"  alt="Left side. "></a
  ><img src="fsm-middle.png" alt=""
  ><a href="?go=right"><img src="fsm-right.png" alt="Right side."></a></p>

4.8.1.1.9 A key part of the content

Status: Last call for comments

In some cases, the image is a critical part of the content. This could be the case, for instance, on a page that is part of a photo gallery. The image is the whole point of the page containing it.

How to provide alternative text for an image that is a key part of the content depends on the image's provenance.

The general case

When it is possible for detailed alternative text to be provided, for example if the image is part of a series of screenshots in a magazine review, or part of a comic strip, or is a photograph in a blog entry about that photograph, text that can serve as a substitute for the image must be given as the contents of the alt attribute.

A screenshot in a gallery of screenshots for a new OS, with some alternative text:

<figure>
 <img src="KDE%20Light%20desktop.png"
      alt="The desktop is blue, with icons along the left hand side in
           two columns, reading System, Home, K-Mail, etc. A window is
           open showing that menus wrap to a second line if they
           cannot fit in the window. The window has a list of icons
           along the top, with an address bar below it, a list of
           icons for tabs along the left edge, a status bar on the
           bottom, and two panes in the middle. The desktop has a bar
           at the bottom of the screen with a few buttons, a pager, a
           list of open applications, and a clock.">
 <figcaption>Screenshot of a KDE desktop.</figcaption>
</figure>

A graph in a financial report:

<img src="sales.gif"
     title="Sales graph"
     alt="From 1998 to 2005, sales increased by the following percentages
     with each year: 624%, 75%, 138%, 40%, 35%, 9%, 21%">

Note that "sales graph" would be inadequate alternative text for a sales graph. Text that would be a good caption is not generally suitable as replacement text.

Images that defy a complete description

In certain cases, the nature of the image might be such that providing thorough alternative text is impractical. For example, the image could be indistinct, or could be a complex fractal, or could be a detailed topographical map.

In these cases, the alt attribute must contain some suitable alternative text, but it may be somewhat brief.

Sometimes there simply is no text that can do justice to an image. For example, there is little that can be said to usefully describe a Rorschach inkblot test. However, a description, even if brief, is still better than nothing:

<figure>
 <img src="/commons/a/a7/Rorschach1.jpg" alt="A shape with left-right
 symmetry with indistinct edges, with a small gap in the center, two
 larger gaps offset slightly from the center, with two similar gaps
 under them. The outline is wider in the top half than the bottom
 half, with the sides extending upwards higher than the center, and
 the center extending below the sides.">
 <figcaption>A black outline of the first of the ten cards
 in the Rorschach inkblot test.</figcaption>
</figure>

Note that the following would be a very bad use of alternative text:

<!-- This example is wrong. Do not copy it. -->
<figure>
 <img src="/commons/a/a7/Rorschach1.jpg" alt="A black outline
 of the first of the ten cards in the Rorschach inkblot test.">
 <figcaption>A black outline of the first of the ten cards
 in the Rorschach inkblot test.</figcaption>
</figure>

Including the caption in the alternative text like this isn't useful because it effectively duplicates the caption for users who don't have images, taunting them twice yet not helping them any more than if they had only read or heard the caption once.

Another example of an image that defies full description is a fractal, which, by definition, is infinite in detail.

The following example shows one possible way of providing alternative text for the full view of an image of the Mandelbrot set.

<img src="ms1.jpeg" alt="The Mandelbrot set appears as a cardioid with
its cusp on the real axis in the positive direction, with a smaller
bulb aligned along the same center line, touching it in the negative
direction, and with these two shapes being surrounded by smaller bulbs
of various sizes.">

Images whose contents are not known

In some unfortunate cases, there might be no alternative text available at all, either because the image is obtained in some automated fashion without any associated alternative text (e.g. a Webcam), or because the page is being generated by a script using user-provided images where the user did not provide suitable or usable alternative text (e.g. photograph sharing sites), or because the author does not himself know what the images represent (e.g. a blind photographer sharing an image on his blog).

In such cases, the alt attribute's value may be omitted, but one of the following conditions must be met as well:

The title attribute is present and has a non-empty value.
The img element is in a figure element that contains a figcaption element that contains content other than inter-element whitespace.
The img element is part of the only paragraph directly in its section, and is the only img element without an alt attribute in its section, and its section has an associated heading.

Such cases are to be kept to an absolute minimum. If there is even the slightest possibility of the author having the ability to provide real alternative text, then it would not be acceptable to omit the alt attribute.

A photo on a photo-sharing site, if the site received the image with no metadata other than the caption:

<figure>
 <img src="1100670787_6a7c664aef.jpg">
 <figcaption>Bubbles traveled everywhere with us.</figcaption>
</figure>

It could also be marked up like this:

<article>
 <h1>Bubbles traveled everywhere with us.</h1>
 <img src="1100670787_6a7c664aef.jpg">
</article>

In either case, though, it would be better if a detailed description of the important parts of the image obtained from the user and included on the page.

A blind user's blog in which a photo taken by the user is shown. Initially, the user might not have any idea what the photo he took shows:

<article>
 <h1>I took a photo</h1>
 <p>I went out today and took a photo!</p>
 <figure>
  <img src="photo2.jpeg">
  <figcaption>A photograph taken blindly from my front porch.</figcaption>
 </figure>
</article>

Eventually though, the user might obtain a description of the image from his friends and could then include alternative text:

<article>
 <h1>I took a photo</h1>
 <p>I went out today and took a photo!</p>
 <figure>
  <img src="photo2.jpeg" alt="The photograph shows my hummingbird
  feeder hanging from the edge of my roof. It is half full, but there
  are no birds around. In the background, out-of-focus trees fill the
  shot. The feeder is made of wood with a metal grate, and it contains
  peanuts. The edge of the roof is wooden too, and is painted white
  with light blue streaks.">
  <figcaption>A photograph taken blindly from my front porch.</figcaption>
 </figure>
</article>

Sometimes the entire point of the image is that a textual description is not available, and the user is to provide the description. For instance, the point of a CAPTCHA image is to see if the user can literally read the graphic. Here is one way to mark up a CAPTCHA (note the title attribute):

<p><label>What does this image say?
<img src="captcha.cgi?id=8934" title="CAPTCHA">
<input type=text name=captcha></label>
(If you cannot see the image, you can use an <a
href="?audio">audio</a> test instead.)</p>

Another example would be software that displays images and asks for alternative text precisely for the purpose of then writing a page with correct alternative text. Such a page could have a table of images, like this:

<table>
 <thead>
  <tr> <th> Image <th> Description
 <tbody>
  <tr>
   <td> <img src="2421.png" title="Image 640 by 100, filename 'banner.gif'">
   <td> <input name="alt2421">
  <tr>
   <td> <img src="2422.png" title="Image 200 by 480, filename 'ad3.gif'">
   <td> <input name="alt2422">
</table>

Notice that even in this example, as much useful information as possible is still included in the title attribute.

Since some users cannot use images at all (e.g. because they have a very slow connection, or because they are using a text-only browser, or because they are listening to the page being read out by a hands-free automobile voice Web browser, or simply because they are blind), the alt attribute is only allowed to be omitted rather than being provided with replacement text when no alternative text is available and none can be made available, as in the above examples. Lack of effort from the part of the author is not an acceptable reason for omitting the alt attribute.

4.8.1.1.10 An image not intended for the user

Status: Last call for comments

Generally authors should avoid using img elements for purposes other than showing images.

If an img element is being used for purposes other than showing an image, e.g. as part of a service to count page views, then the alt attribute must be the empty string.

In such cases, the width and height attributes should both be set to zero.

4.8.1.1.11 An image in an e-mail or private document intended for a specific person who is known to be able to view images

Status: Last call for comments

This section does not apply to documents that are publicly accessible, or whose target audience is not necessarily personally known to the author, such as documents on a Web site, e-mails sent to public mailing lists, or software documentation.

When an image is included in a private communication (such as an HTML e-mail) aimed at a specific person who is known to be able to view images, the alt attribute may be omitted. However, even in such cases it is strongly recommended that alternative text be included (as appropriate according to the kind of image involved, as described in the above entries), so that the e-mail is still usable should the user use a mail client that does not support images, or should the document be forwarded on to other users whose abilities might not include easily seeing images.

4.8.1.1.12 General guidelines

Status: Last call for comments

The most general rule to consider when writing alternative text is the following: the intent is that replacing every image with the text of its alt attribute not change the meaning of the page.

So, in general, alternative text can be written by considering what one would have written had one not been able to include the image.

A corollary to this is that the alt attribute's value should never contain text that could be considered the image's caption, title, or legend. It is supposed to contain replacement text that could be used by users instead of the image; it is not meant to supplement the image. The title attribute can be used for supplemental information.

One way to think of alternative text is to think about how you would read the page containing the image to someone over the phone, without mentioning that there is an image present. Whatever you say instead of the image is typically a good start for writing the alternative text.

4.8.1.1.13 Guidance for markup generators

Status: Last call for comments

Markup generators (such as WYSIWYG authoring tools) should, wherever possible, obtain alternative text from their users. However, it is recognized that in many cases, this will not be possible.

For images that are the sole contents of links, markup generators should examine the link target to determine the title of the target, or the URL of the target, and use information obtained in this manner as the alternative text.

As a last resort, implementors should either set the alt attribute to the empty string, under the assumption that the image is a purely decorative image that doesn't add any information but is still specific to the surrounding content, or omit the alt attribute altogether, under the assumption that the image is a key part of the content.

Markup generators should generally avoid using the image's own file name as the alternative text. Similarly, markup generators should avoid generating alternative text from any content that will be equally available to presentation user agents (e.g. Web browsers).

This is because once a page is generated, it will typically not be updated, whereas the browsers that later read the page can be updated by the user, therefore the browser is likely to have more up-to-date and finely-tuned heuristics than the markup generator did when generating the page.

4.8.1.1.14 Guidance for conformance checkers

Status: Last call for comments

A conformance checker must report the lack of an alt attribute as an error unless one of the conditions listed below applies:

The title attribute is present and has a non-empty value (as described above).
The img element is in a figure element that contains a figcaption element that contains content other than inter-element whitespace (as described above).
The img element is part of the only paragraph directly in its section, and is the only img element without an alt attribute in its section, and its section has an associated heading (as described above).
The conformance checker has been configured to assume that the document is an e-mail or document intended for a specific person who is known to be able to view images.
The document has a meta element with a name attribute whose value is an ASCII case-insensitive match for the string "generator". (This case does not represent a case where the document is conforming, only that the generator could not determine appropriate alternative text — validators are required to not show an error in this case to discourage markup generators from including bogus alternative text purely in an attempt to silence validators.)

4.8.2 The `iframe` element

Status: Last call for comments. ISSUE-100 (srcdoc) and ISSUE-103 (srcdoc-xml-escaping) block progress to Last Call

Categories

Contexts in which this element may be used:

Where embedded content is expected.

Content model:

Text that conforms to the requirements given in the prose.

Content attributes:

src

srcdoc

name

sandbox

seamless

width

height

DOM interface:

interface HTMLIFrameElement : HTMLElement {
           attribute DOMString src;
           attribute DOMString srcdoc;
           attribute DOMString name;
  [PutForwards=value] readonly attribute DOMSettableTokenList sandbox;
           attribute boolean seamless;
           attribute DOMString width;
           attribute DOMString height;
  readonly attribute Document contentDocument;
  readonly attribute WindowProxy contentWindow;
};

The iframe element represents a nested browsing context.

The src attribute gives the address of a page that the nested browsing context is to contain. The attribute, if present, must be a valid URL.

The srcdoc attribute gives the content of the page that the nested browsing context is to contain. The value of the attribute in is an iframe srcdoc document.

For iframe elements in HTML documents, the attribute, if present, must have a value using the HTML syntax that consists of the following syntactic components, in the given order:

Any number of comments and space characters.
Optionally, a DOCTYPE.
Any number of comments and space characters.
The root element, in the form of an html element.
Any number of comments and space characters.

For iframe elements in XML documents, the attribute, if present, must have a value that matches the production labeled document in the XML specification. [XML]

If the src attribute and the srcdoc attribute are both specified together, the srcdoc attribute takes priority. This allows authors to provide a fallback URL for legacy user agents that do not support the srcdoc attribute.

When an iframe element is first inserted into a document, the user agent must create a nested browsing context, and then process the iframe attributes for the first time.

Whenever an iframe element with a nested browsing context has its srcdoc attribute set or changed, the user agent must process the iframe attributes.

Similarly, whenever an iframe element with a nested browsing context but with no srcdoc attribute specified has its src attribute set or changed, the user agent must process the iframe attributes.

When the user agent is to process the iframe attributes, it must run the first appropriate steps from the following list:

If the srcdoc attribute is specified

Navigate the element's browsing context to a resource whose Content-Type is text/html, whose URL is about:srcdoc, and whose data consists of the value of the attribute.

If the src attribute is specified but the srcdoc attribute is not

Resolve the value of the src attribute, relative to the iframe element.
If that is not successful, then jump to the empty step below.
If the resulting absolute URL is an ASCII case-insensitive match for the string "about:blank", and the user agent is processing this iframe's attributes for the first time, then jump to the empty step below. (In cases other than the first time, about:blank is loaded normally.)
Navigate the element's browsing context to the resulting absolute URL.

Empty: When the steps above require the user agent to jump to the empty step, if the user agent is processing this iframe's attributes for the first time, then the user agent must queue a task to fire a simple event named load at the iframe element. (After jumping to this step, the above steps are not resumed.)

Otherwise

Queue a task to fire a simple event named load at the iframe element.

Any navigation required of the user agent in the process the iframe attributes algorithm must be completed with the iframe element's document's browsing context as the source browsing context.

Furthermore, if the process the iframe attributes algorithm was invoked for the first time for this element (i.e. as a result of the element being inserted into a document), then any navigation required of the user agent in that algorithm must be completed with replacement enabled.

If, when the element is created, the srcdoc attribute is not set, and the src attribute is either also not set or set but its value cannot be resolved, the browsing context will remain at the initial about:blank page.

If the user navigates away from this page, the iframe's corresponding WindowProxy object will proxy new Window objects for new Document objects, but the src attribute will not change.

Here a blog uses the srcdoc attribute in conjunction with the sandbox and seamless attributes described below to provide users of user agents that support this feature with an extra layer of protection from script injection in the blog post comments:

<article>
 <h1>I got my own magazine!</h1>
 <p>After much effort, I've finally found a publisher, and so now I
 have my own magazine! Isn't that awesome?! The first issue will come
 out in September, and we have articles about getting food, and about
 getting in boxes, it's going to be great!</p>
 <footer>
  <p>Written by <a href="/users/cap">cap</a>.
  <time pubdate>2009-08-21T23:32Z</time></p>
 </footer>
 <article>
  <footer> At <time pubdate>2009-08-21T23:35Z</time>, <a href="/users/ch">ch</a> writes: </footer>
  <iframe seamless sandbox="allow-same-origin" srcdoc="<p>did you get a cover picture yet?"></iframe>
 </article>
 <article>
  <footer> At <time pubdate>2009-08-21T23:44Z</time>, <a href="/users/cap">cap</a> writes: </footer>
  <iframe seamless sandbox="allow-same-origin" srcdoc="<p>Yeah, you can see it <a href=&quot;/gallery?mode=cover&amp;amp;page=1&quot;>in my gallery</a>."></iframe>
 </article>
 <article>
  <footer> At <time pubdate>2009-08-21T23:58Z</time>, <a href="/users/ch">ch</a> writes: </footer>
  <iframe seamless sandbox="allow-same-origin" srcdoc="<p>hey that's earl's table.
<p>you should get earl&amp;amp;me on the next cover."></iframe>
 </article>

Notice the way that quotes have to be escaped (otherwise the sandbox attribute would end prematurely), and the way raw ampersands (e.g. in URLs or in prose) mentioned in the sandboxed content have to be doubly escaped — once so that the ampersand is preserved when originally parsing the sandbox attribute, and once more to prevent the ampersand from being misinterpreted when parsing the sandboxed content.

In the HTML syntax, authors need only remember to use U+0022 QUOTATION MARK characters (") to wrap the attribute contents and then to escape all U+0022 QUOTATION MARK (") and U+0026 AMPERSAND (&) characters, and to specify the sandbox attribute, to ensure safe embedding of content.

Due to restrictions of the XML syntax, in XML a number of other characters need to be escaped also to ensure correctness.

The name attribute, if present, must be a valid browsing context name. The given value is used to name the nested browsing context. When the browsing context is created, if the attribute is present, the browsing context name must be set to the value of this attribute; otherwise, the browsing context name must be set to the empty string.

Whenever the name attribute is set, the nested browsing context's name must be changed to the new value. If the attribute is removed, the browsing context name must be set to the empty string.

When content loads in an iframe, after any load events are fired within the content itself, the user agent must queue a task to fire a simple event named load at the iframe element. When content fails to load (e.g. due to a network error), then the user agent must queue a task to fire a simple event named error at the element instead.

The task source for these tasks is the DOM manipulation task source.

A load event is also fired at the iframe element when it is created if no other data is loaded in it.

When there is an active parser in the iframe, and when anything in the iframe is delaying the load event of the iframe's browsing context's active document, the iframe must delay the load event of its document.

If, during the handling of the load event, the browsing context in the iframe is again navigated, that will further delay the load event.

The sandbox attribute, when specified, enables a set of extra restrictions on any content hosted by the iframe. Its value must be an unordered set of unique space-separated tokens. The allowed values are allow-same-origin, allow-forms, and allow-scripts. When the attribute is set, the content is treated as being from a unique origin, forms and scripts are disabled, links are prevented from targeting other browsing contexts, and plugins are disabled. The allow-same-origin keyword allows the content to be treated as being from the same origin instead of forcing it into a unique origin, and the allow-forms and allow-scripts keywords re-enable forms and scripts respectively (though scripts are still prevented from creating popups).

Setting both the allow-scripts and allow-same-origin keywords together when the embedded page has the same origin as the page containing the iframe allows the embedded page to simply remove the sandbox attribute.

Sandboxing hostile content is of minimal help if an attacker can convince the user to just visit the hostile content directly, rather than in the iframe. To limit the damage that can be caused by hostile HTML content, it should be served using the text/html-sandboxed MIME type.

While the sandbox attribute is specified, the iframe element's nested browsing context must have the flags given in the following list set. In addition, any browsing contexts nested within an iframe, either directly or indirectly, must have all the flags set on them as were set on the iframe's Document's browsing context when the iframe's Document was created.

The sandboxed navigation browsing context flag

This flag prevents content from navigating browsing contexts other than the sandboxed browsing context itself (or browsing contexts further nested inside it).

This flag also prevents content from creating new auxiliary browsing contexts, e.g. using the target attribute or the window.open() method.

The sandboxed plugins browsing context flag

This flag prevents content from instantiating plugins, whether using the embed element, the object element, the applet element, or through navigation of a nested browsing context.

The sandboxed seamless iframes flag

This flag prevents content from using the seamless attribute on descendant iframe elements.

This prevents a page inserted using the allow-same-origin keyword from using a CSS-selector-based method of probing the DOM of other pages on the same site (in particular, pages that contain user-sensitive information).

The sandboxed origin browsing context flag, unless the sandbox attribute's value, when split on spaces, is found to have the allow-same-origin keyword set

This flag forces content into a unique origin, thus preventing it from accessing other content from the same origin.

This flag also prevents script from reading from or writing to the document.cookie IDL attribute, and blocks access to localStorage and openDatabase(). [WEBSTORAGE] [WEBSQL]

The allow-same-origin attribute is intended for two cases.

First, it can be used to allow content from the same site to be sandboxed to disable scripting, while still allowing access to the DOM of the sandboxed content.

Second, it can be used to embed content from a third-party site, sandboxed to prevent that site from opening popup windows, etc, without preventing the embedded page from communicating back to its originating site, using the database APIs to store data, etc.

The sandboxed forms browsing context flag, unless the sandbox attribute's value, when split on spaces, is found to have the allow-forms keyword set

This flag blocks form submission.

The sandboxed scripts browsing context flag, unless the sandbox attribute's value, when split on spaces, is found to have the allow-scripts keyword set

This flag blocks script execution.

These flags must not be set unless the conditions listed above define them as being set.

These flags only take effect when the nested browsing context of the iframe is navigated. Removing then, or removing the entire sandbox attribute, has no effect on an already-loaded page.

In this example, some completely-unknown, potentially hostile, user-provided HTML content is embedded in a page. Because it is sandboxed, it is treated by the user agent as being from a unique origin, despite the content being served from the same site. Thus it is affected by all the normal cross-site restrictions. In addition, the embedded page has scripting disabled, plugins disabled, forms disabled, and it cannot navigate any frames or windows other than itself (or any frames or windows it itself embeds).

<p>We're not scared of you! Here is your content, unedited:</p>
<iframe sandbox src="getusercontent.cgi?id=12193"></iframe>

Note that cookies are still sent to the server in the getusercontent.cgi request, though they are not visible in the document.cookie IDL attribute.

It is important that the server serve the user-provided HTML using the text/html-sandboxed MIME type so that if the attacker convinces the user to visit that page directly, the page doesn't run in the context of the site's origin, which would make the user vulnerable to any attack found in the page.

In this example, a gadget from another site is embedded. The gadget has scripting and forms enabled, and the origin sandbox restrictions are lifted, allowing the gadget to communicate with its originating server. The sandbox is still useful, however, as it disables plugins and popups, thus reducing the risk of the user being exposed to malware and other annoyances.

<iframe sandbox="allow-same-origin allow-forms allow-scripts"
        src="http://maps.example.com/embedded.html"></iframe>

Suppose a file A contained the following fragment:

<iframe sandbox="allow-same-origin allow-forms" src=B></iframe>

Suppose that file B contained an iframe also:

<iframe sandbox="allow-scripts" src=C></iframe>

Further, suppose that file C contained a link:

<a href=D>Link</a>

For this example, suppose all the files were served as text/html.

Page C in this scenario has all the sandboxing flags set. Scripts are disabled, because the iframe in A has scripts disabled, and this overrides the allow-scripts keyword set on the iframe in B. Forms are also disabled, because the inner iframe (in B) does not have the allow-forms keyword set.

Suppose now that a script in A removes all the sandbox attributes in A and B. This would change nothing immediately. If the user clicked the link in C, loading page D into the iframe in B, page D would now act as if the iframe in B had the allow-same-origin and allow-forms keywords set, because that was the state of the nested browsing context in the iframe in A when page B was loaded.

Generally speaking, dynamically removing or changing the sandbox attribute is ill-advised, because it can make it quite hard to reason about what will be allowed and what will not.

Potentially hostile files can be served from the same server as the file containing the iframe element by labeling them as text/html-sandboxed instead of text/html. This ensures that scripts in the files are unable to attack the site (as if they were actually served from another server), even if the user is tricked into visiting those pages directly, without the protection of the sandbox attribute.

If the allow-scripts keyword is set along with allow-same-origin keyword, and the file is from the same origin as the iframe's Document, then a script in the "sandboxed" iframe could just reach out, remove the sandbox attribute, and then reload itself, effectively breaking out of the sandbox altogether.

The seamless attribute is a boolean attribute. When specified, it indicates that the iframe element's browsing context is to be rendered in a manner that makes it appear to be part of the containing document (seamlessly included in the parent document). Specifically, when the attribute is set on an iframe element whose owner Document's browsing context did not have the sandboxed seamless iframes flag set when that Document was created, and while either the browsing context's active document has the same origin as the iframe element's document, or the browsing context's active document's address has the same origin as the iframe element's document, the following requirements apply:

The user agent must set the seamless browsing context flag to true for that browsing context. This will cause links to open in the parent browsing context.
In a CSS-supporting user agent: the user agent must add all the style sheets that apply to the iframe element to the cascade of the active document of the iframe element's nested browsing context, at the appropriate cascade levels, before any style sheets specified by the document itself.
In a CSS-supporting user agent: the user agent must, for the purpose of CSS property inheritance only, treat the root element of the active document of the iframe element's nested browsing context as being a child of the iframe element. (Thus inherited properties on the root element of the document in the iframe will inherit the computed values of those properties on the iframe element instead of taking their initial values.)
In visual media, in a CSS-supporting user agent: the user agent should set the intrinsic width of the iframe to the width that the element would have if it was a non-replaced block-level element with 'width: auto'.
In visual media, in a CSS-supporting user agent: the user agent should set the intrinsic height of the iframe to the height of the bounding box around the content rendered in the iframe at its current width (as given in the previous bullet point), as it would be if the scrolling position was such that the top of the viewport for the content rendered in the iframe was aligned with the origin of that content's canvas.
In visual media, in a CSS-supporting user agent: the user agent must force the height of the initial containing block of the active document of the nested browsing context of the iframe to zero.

This is intended to get around the otherwise circular dependency of percentage dimensions that depend on the height of the containing block, thus affecting the height of the document's bounding box, thus affecting the height of the viewport, thus affecting the size of the initial containing block.
In speech media, the user agent should render the nested browsing context without announcing that it is a separate document.
User agents should, in general, act as if the active document of the iframe's nested browsing context was part of the document that the iframe is in.

For example if the user agent supports listing all the links in a document, links in "seamlessly" nested documents would be included in that list without being significantly distinguished from links in the document itself.

If the attribute is not specified, or if the origin conditions listed above are not met, then the user agent should render the nested browsing context in a manner that is clearly distinguishable as a separate browsing context, and the seamless browsing context flag must be set to false for that browsing context.

It is important that user agents recheck the above conditions whenever the active document of the nested browsing context of the iframe changes, such that the seamless browsing context flag gets unset if the nested browsing context is navigated to another origin.

The attribute can be set or removed dynamically, with the rendering updating in tandem.

In this example, the site's navigation is embedded using a client-side include using an iframe. Any links in the iframe will, in new user agents, be automatically opened in the iframe's parent browsing context; for legacy user agents, the site could also include a base element with a target attribute with the value _parent. Similarly, in new user agents the styles of the parent page will be automatically applied to the contents of the frame, but to support legacy user agents authors might wish to include the styles explicitly.

<nav><iframe seamless src="nav.include.html"></iframe></nav>

The iframe element supports dimension attributes for cases where the embedded content has specific dimensions (e.g. ad units have well-defined dimensions).

An iframe element never has fallback content, as it will always create a nested browsing context, regardless of whether the specified initial contents are successfully used.

Descendants of iframe elements represent nothing. (In legacy user agents that do not support iframe elements, the contents would be parsed as markup that could act as fallback content.)

When used in HTML documents, the allowed content model of iframe elements is text, except that invoking the HTML fragment parsing algorithm with the iframe element as the context element and the text contents as the input must result in a list of nodes that are all phrasing content, with no parse errors having occurred, with no script elements being anywhere in the list or as descendants of elements in the list, and with all the elements in the list (including their descendants) being themselves conforming.

The iframe element must be empty in XML documents.

The HTML parser treats markup inside iframe elements as text.

The IDL attributes src, srcdoc, name, sandbox, and seamless must reflect the respective content attributes of the same name.

The contentDocument IDL attribute must return the Document object of the active document of the iframe element's nested browsing context.

The contentWindow IDL attribute must return the WindowProxy object of the iframe element's nested browsing context.

Here is an example of a page using an iframe to include advertising from an advertising broker:

<iframe src="http://ads.example.com/?customerid=923513721&amp;format=banner"
        width="468" height="60"></iframe>

4.8.3 The `embed` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where embedded content is expected.

Content model:

Empty.

Content attributes:

src

type

width

height

Any other attribute that has no namespace (see prose).

DOM interface:

interface HTMLEmbedElement : HTMLElement {
           attribute DOMString src;
           attribute DOMString type;
           attribute DOMString width;
           attribute DOMString height;
};

Depending on the type of content instantiated by the embed element, the node may also support other interfaces.

The embed element represents an integration point for an external (typically non-HTML) application or interactive content.

The src attribute gives the address of the resource being embedded. The attribute, if present, must contain a valid URL.

The type attribute, if present, gives the MIME type by which the plugin to instantiate is selected. The value must be a valid MIME type. If both the type attribute and the src attribute are present, then the type attribute must specify the same type as the explicit Content-Type metadata of the resource given by the src attribute.

When the element is created with neither a src attribute nor a type attribute, and when attributes are removed such that neither attribute is present on the element anymore, and when the element has a media element ancestor, and when the element has an ancestor object element that is not showing its fallback content, any plugins instantiated for the element must be removed, and the embed element represents nothing.

If either:

the sandboxed plugins browsing context flag was set on the browsing context for which the embed element's Document is the active document when that Document was created, or
the embed element's Document was parsed from a resource whose sniffed type as determined during navigation is text/html-sandboxed

...then the user agent must render the embed element in a manner that conveys that the plugin was disabled. The user agent may offer the user the option to override the sandbox and instantiate the plugin anyway; if the user invokes such an option, the user agent must act as if the conditions above did not apply for the purposes of this element.

Plugins are disabled in sandboxed browsing contexts because they might not honor the restrictions imposed by the sandbox (e.g. they might allow scripting even when scripting in the sandbox is disabled). User agents should convey the danger of overriding the sandbox to the user if an option to do so is provided.

An embed element is said to be potentially active when the following conditions are all met simultaneously:

The element is in a Document.
The element's Document is fully active.
The element has either a src attribute set or a type attribute set (or both).
The element is not in a Document whose browsing context had the sandboxed plugins browsing context flag set when the Document was created (unless this has been overrriden as described above).
The element's Document was not parsed from a resource whose sniffed type as determined during navigation is text/html-sandboxed (unless this has been overrriden as described above).
The element is not a descendant of a media element.
The element is not a descendant of an object element that is not showing its fallback content.

Whenever an embed element that was not potentially active becomes potentially active, and whenever a potentially active embed element's src attribute is set, changed, or removed, and whenever a potentially active embed element's type attribute is set, changed, or removed, the appropriate set of steps from the following is then applied:

If the element has a src attribute set

The user agent must resolve the value of the element's src attribute, relative to the element. If that is successful, the user agent should fetch the resulting absolute URL, from the element's browsing context scope origin if it has one. The task that is queued by the networking task source once the resource has been fetched must find and instantiate an appropriate plugin based on the content's type, and hand that plugin the content of the resource, replacing any previously instantiated plugin for the element.

Fetching the resource must delay the load event of the element's document.

If the element has no src attribute set

The user agent should find and instantiate an appropriate plugin based on the value of the type attribute.

Whenever an embed element that was potentially active stops being potentially active, any plugin that had been instantiated for that element must be unloaded.

The embed element is unaffected by the CSS 'display' property. The selected plugin is instantiated even if the element is hidden with a 'display:none' CSS style.

The type of the content being embedded is defined as follows:

If the element has a type attribute, and that attribute's value is a type that a plugin supports, then the value of the type attribute is the content's type.
Otherwise, if the <path> component of the URL of the specified resource (after any redirects) matches a pattern that a plugin supports, then the content's type is the type that that plugin can handle.

For example, a plugin might say that it can handle resources with <path> components that end with the four character string ".swf".
Otherwise, if the specified resource has explicit Content-Type metadata, then that is the content's type.
Otherwise, the content has no type and there can be no appropriate plugin for it.

The embed element has no fallback content. If the user agent can't find a suitable plugin, then the user agent must use a default plugin. (This default could be as simple as saying "Unsupported Format".)

Whether the resource is fetched successfully or not (e.g. whether the response code was a 2xx code or equivalent) must be ignored when determining the resource's type and when handing the resource to the plugin.

This allows servers to return data for plugins even with error responses (e.g. HTTP 500 Internal Server Error codes can still contain plugin data).

Any namespace-less attribute other than name and align may be specified on the embed element, so long as its name is XML-compatible and contains no characters in the range U+0041 to U+005A (LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z). These attributes are then passed as parameters to the plugin.

All attributes in HTML documents get lowercased automatically, so the restriction on uppercase letters doesn't affect such documents.

The two exceptions are to exclude legacy attributes that have side-effects beyond just sending parameters to the plugin.

The user agent should pass the names and values of all the attributes of the embed element that have no namespace to the plugin used, when it is instantiated.

If the plugin instantiated for the embed element supports a scriptable interface, the HTMLEmbedElement object representing the element should expose that interface while the element is instantiated.

The embed element supports dimension attributes.

The IDL attributes src and type each must reflect the respective content attributes of the same name.

Here's a way to embed a resource that requires a proprietary plug-in, like Flash:

<embed src="catgame.swf">

If the user does not have the plug-in (for example if the plug-in vendor doesn't support the user's platform), then the user will be unable to use the resource.

To pass the plugin a parameter "quality" with the value "high", an attribute can be specified:

<embed src="catgame.swf" quality="high">

This would be equivalent to the following, when using an object element instead:

<object data="catgame.swf">
 <param name="quality" value="high">
</object>

4.8.4 The `object` element

Status: Last call for comments

Categories

If the element has a usemap attribute: Interactive content.

Listed, submittable, form-associated element.

Contexts in which this element may be used:

Where embedded content is expected.

Content model:

Zero or more param elements, then, transparent.

Content attributes:

data

type

name

usemap

form

width

height

DOM interface:

interface HTMLObjectElement : HTMLElement {
           attribute DOMString data;
           attribute DOMString type;
           attribute DOMString name;
           attribute DOMString useMap;
  readonly attribute HTMLFormElement form;
           attribute DOMString width;
           attribute DOMString height;
  readonly attribute Document contentDocument;
  readonly attribute WindowProxy contentWindow;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);
};

Depending on the type of content instantiated by the object element, the node also supports other interfaces.

The object element can represent an external resource, which, depending on the type of the resource, will either be treated as an image, as a nested browsing context, or as an external resource to be processed by a plugin.

The data attribute, if present, specifies the address of the resource. If present, the attribute must be a valid URL.

The type attribute, if present, specifies the type of the resource. If present, the attribute must be a valid MIME type.

At least one of either the data attribute or the type attribute must be present.

The name attribute, if present, must be a valid browsing context name. The given value is used to name the nested browsing context, if applicable.

When the element is created, when it is popped off the stack of open elements of an HTML parser or XML parser, and subsequently whenever the element is inserted into a document or removed from a document; and whenever the element's Document changes whether it is fully active; and whenever an ancestor object element changes to or from showing its fallback content; and whenever the element's classid attribute is set, changed, or removed; and, when its classid attribute is not present, whenever its data attribute is set, changed, or removed; and, when neither its classid attribute nor its data attribute are present, whenever its type attribute is set, changed, or removed: the user agent must queue a task to run the following steps to (re)determine what the object element represents. The task source for this task is the DOM manipulation task source.

If the user has indicated a preference that this object element's fallback content be shown instead of the element's usual behavior, then jump to the last step in the overall set of steps (fallback).

For example, a user could ask for the element's fallback content to be shown because that content uses a format that the user finds more accessible.
If the element has an ancestor media element, or has an ancestor object element that is not showing its fallback content, or if the element is not in a Document with a browsing context, or if the element's Document is not fully active, or if the element is still in the stack of open elements of an HTML parser or XML parser, then jump to the last step in the overall set of steps (fallback).
If the classid attribute is present, and has a value that isn't the empty string, then: if the user agent can find a plugin suitable according to the value of the classid attribute, and plugins aren't being sandboxed, then that plugin should be used, and the value of the data attribute, if any, should be passed to the plugin. If no suitable plugin can be found, or if the plugin reports an error, jump to the last step in the overall set of steps (fallback).
If the data attribute is present and its value is not the empty string, then:
1. If the type attribute is present and its value is not a type that the user agent supports, and is not a type that the user agent can find a plugin for, then the user agent may jump to the last step in the overall set of steps (fallback) without fetching the content to examine its real type.
2. Resolve the URL specified by the data attribute, relative to the element.
3. If that failed, fire a simple event named error at the element, then jump to the last step in the overall set of steps (fallback).
4. Fetch the resulting absolute URL, from the element's browsing context scope origin if it has one.
  
  Fetching the resource must delay the load event of the element's document until the task that is queued by the networking task source once the resource has been fetched (defined next) has been run.
5. If the resource is not yet available (e.g. because the resource was not available in the cache, so that loading the resource required making a request over the network), then jump to the last step in the overall set of steps (fallback). The task that is queued by the networking task source once the resource is available must restart this algorithm from this step. Resources can load incrementally; user agents may opt to consider a resource "available" whenever enough data has been obtained to begin processing the resource.
6. If the load failed (e.g. there was an HTTP 404 error, there was a DNS error), fire a simple event named error at the element, then jump to the last step in the overall set of steps (fallback).
7. Determine the resource type, as follows:
  1. Let the resource type be unknown.
  2. Let the sniffed flag be false.
  3. If the user agent is configured to strictly obey Content-Type headers for this resource, and the resource has associated Content-Type metadata, then let the resource type be the type specified in the resource's Content-Type metadata, and abort these substeps.
  4. If there is a type attribute present on the object element, and that attribute's value is not a type that the user agent supports, but it is a type that a plugin supports, then let the resource type be the type specified in that type attribute.
  5. Otherwise, if the resource type is unknown, and the resource has associated Content-Type metadata, then let the resource type be the type specified in the resource's Content-Type metadata.
    
    If this results in the resource type being "text/plain", then let the resource type be the result of applying the rules for distingushing if a resource is text or binary to the resource instead, and then set the sniffed flag to true.
  6. If the resource type is unknown or "application/octet-stream" at this point and there is a type attribute present on the object element, then change the resource type to instead be the type specified in that type attribute.
    
    Otherwise, if the resource type is "application/octet-stream" but there is no type attribute on the object element, then change the resource type to be unknown, so that the sniffing rules in the following steps are invoked.
  7. If the resource type is still unknown at this point, but the <path> component of the URL of the specified resource (after any redirects) matches a pattern that a plugin supports, then let resource type be the type that that plugin can handle.
    
    For example, a plugin might say that it can handle resources with <path> components that end with the four character string ".swf".
  8. If the resource type is still unknown, and the sniffed flag is false, then change the resource type to instead be the sniffed type of the resource.
    
    Otherwise, if the resource type is still unknown, and the sniffed flag is true, then change the resource type back to text/plain.
8. Handle the content as given by the first of the following cases that matches:
  
  If the resource type is not a type that the user agent supports, but it is a type that a plugin supports
  
  If plugins are being sandboxed, jump to the last step in the overall set of steps (fallback).
  
  Otherwise, the user agent should use the plugin that supports resource type and pass the content of the resource to that plugin. If the plugin reports an error, then jump to the last step in the overall set of steps (fallback).
  
  If the resource type is an XML MIME type, or if the resource type does not start with "image/"
  
  The object element must be associated with a newly created nested browsing context, if it does not already have one.
  
  If the URL of the given resource is not about:blank, the element's nested browsing context must then be navigated to that resource, with replacement enabled, and with the object element's document's browsing context as the source browsing context. (The data attribute of the object element doesn't get updated if the browsing context gets further navigated to other locations.)
  
  If the URL of the given resource is about:blank, then, instead, the user agent must queue a task to fire a simple event named load at the object element.
  
  The object element represents the nested browsing context.
  
  If the name attribute is present, the browsing context name must be set to the value of this attribute; otherwise, the browsing context name must be set to the empty string.
  
  It's possible that the navigation of the browsing context will actually obtain the resource from a different application cache. Even if the resource is then found to have a different type, it is still used as part of a nested browsing context; this algorithm doesn't restart with the new resource.
  
  If the resource type starts with "image/", and support for images has not been disabled
  
  Apply the image sniffing rules to determine the type of the image.
  
  The object element represents the specified image. The image is not a nested browsing context.
  
  If the image cannot be rendered, e.g. because it is malformed or in an unsupported format, jump to the last step in the overall set of steps (fallback).
  
  Otherwise
  
  The given resource type is not supported. Jump to the last step in the overall set of steps (fallback).
9. The element's contents are not part of what the object element represents.
10. Once the resource is completely loaded, queue a task to fire a simple event named load at the element.
  
  The task source for this task is the DOM manipulation task source.
If the data attribute is absent but the type attribute is present, plugins aren't being sandboxed, and the user agent can find a plugin suitable according to the value of the type attribute, then that plugin should be used. If no suitable plugin can be found, or if the plugin reports an error, jump to the next step (fallback).
(Fallback.) The object element represents the element's children, ignoring any leading param element children. This is the element's fallback content. If the element has an instantiated plugin, then unload it.

When the algorithm above instantiates a plugin, the user agent should pass to the plugin used the names and values of all the attributes on the element, in the order they were added to the element, with the attributes added by the parser being ordered in source order, followed by a parameter named "PARAM" whose value is null, followed by all the names and values of parameters given by param elements that are children of the object element, in tree order. If the plugin supports a scriptable interface, the HTMLObjectElement object representing the element should expose that interface. The object element represents the plugin. The plugin is not a nested browsing context.

If either:

the sandboxed plugins browsing context flag was set on the object element's Document's browsing context when the Document was created, or
the object element's Document was parsed from a resource whose sniffed type as determined during navigation is text/html-sandboxed

...then the steps above must always act as if they had failed to find a plugin, even if one would otherwise have been used.

The above algorithm is independent of CSS properties (including 'display', 'overflow', and 'visibility'). For example, it runs even if the element is hidden with a 'display:none' CSS style, and does not run again if the element's visibility changes.

Due to the algorithm above, the contents of object elements act as fallback content, used only when referenced resources can't be shown (e.g. because it returned a 404 error). This allows multiple object elements to be nested inside each other, targeting multiple user agents with different capabilities, with the user agent picking the first one it supports.

Whenever the name attribute is set, if the object element has a nested browsing context, its name must be changed to the new value. If the attribute is removed, if the object element has a browsing context, the browsing context name must be set to the empty string.

The usemap attribute, if present while the object element represents an image, can indicate that the object has an associated image map. The attribute must be ignored if the object element doesn't represent an image.

The form attribute is used to explicitly associate the object element with its form owner.

Constraint validation: object elements are always barred from constraint validation.

The object element supports dimension attributes.

The IDL attributes data, type, name, and useMap each must reflect the respective content attributes of the same name.

The contentDocument IDL attribute must return the Document object of the active document of the object element's nested browsing context, if it has one; otherwise, it must return null.

The contentWindow IDL attribute must return the WindowProxy object of the object element's nested browsing context, if it has one; otherwise, it must return null.

The willValidate, validity, and validationMessage attributes, and the checkValidity() and setCustomValidity() methods, are part of the constraint validation API.

In the following example, a Java applet is embedded in a page using the object element. (Generally speaking, it is better to avoid using applets like these and instead use native JavaScript and HTML to provide the functionality, since that way the application will work on all Web browsers without requiring a third-party plugin. Many devices, especially embedded devices, do not support third-party technologies like Java.)

<figure>
 <object type="application/x-java-applet">
  <param name="code" value="MyJavaClass">
  <p>You do not have Java available, or it is disabled.</p>
 </object>
 <figcaption>My Java Clock</figcaption>
</figure>

In this example, an HTML page is embedded in another using the object element.

<figure>
 <object data="clock.html"></object>
 <figcaption>My HTML Clock</figcaption>
</figure>

The following example shows how a plugin can be used in HTML (in this case the Flash plugin, to show a video file). Fallback is provided for users who do not have Flash enabled, in this case using the video element to show the video for those using user agents that support video, and finally providing a link to the video for those who have neither Flash nor a video-capable browser.

<p>Look at my video:
 <object type="application/x-shockwave-flash">
  <param name=movie value="http://video.example.com/library/watch.swf">
  <param name=allowfullscreen value=true>
  <param name=flashvars value="http://video.example.com/vids/315981">
  <video controls src="http://video.example.com/vids/315981">
   <a href="http://video.example.com/vids/315981">View video</a>.
  </video>
 </object> 
</p>

4.8.5 The `param` element

Status: Last call for comments

Categories

None.

Contexts in which this element may be used:

As a child of an object element, before any flow content.

Content model:

Empty.

Content attributes:

name

value

DOM interface:

interface HTMLParamElement : HTMLElement {
           attribute DOMString name;
           attribute DOMString value;
};

The param element defines parameters for plugins invoked by object elements. It does not represent anything on its own.

The name attribute gives the name of the parameter.

The value attribute gives the value of the parameter.

Both attributes must be present. They may have any value.

If both attributes are present, and if the parent element of the param is an object element, then the element defines a parameter with the given name/value pair.

The IDL attributes name and value must both reflect the respective content attributes of the same name.

The following example shows how the param element can be used to pass a parameter to a plugin, in this case the O3D plugin.

<!DOCTYPE HTML>
<html lang="en">
 <head>
  <title>O3D test page</title>
 </head>
 <body>
  <p>
   <object type="application/vnd.o3d.auto">
    <param name="o3d_features" value="FloatingPointTextures">
    This page requires the use of a proprietary technology. Since you
    have not installed the software product required to view this
    page, you should try visiting another site that instead uses open
    vendor-neutral technologies.
   </object>
   <script src="o3dtest.js"></script>
  </p>
 </body>
</html>

4.8.6 The `video` element

Status: Last call for comments. ISSUE-9 (video-accessibility) blocks progress to Last Call

Categories

If the element has a controls attribute: Interactive content.

Contexts in which this element may be used:

Where embedded content is expected.

Content model:

If the element has a src attribute: transparent, but with no media element descendants.

If the element does not have a src attribute: one or more source elements, then, transparent, but with no media element descendants.

Content attributes:

src

poster

preload

autoplay

loop

controls

width

height

DOM interface:

interface HTMLVideoElement : HTMLMediaElement {
           attribute DOMString width;
           attribute DOMString height;
  readonly attribute unsigned long videoWidth;
  readonly attribute unsigned long videoHeight;
           attribute DOMString poster;
};

A video element is used for playing videos or movies.

Content may be provided inside the video element. User agents should not show this content to the user; it is intended for older Web browsers which do not support video, so that legacy video plugins can be tried, or to show text to the users of these older browsers informing them of how to access the video contents.

In particular, this content is not intended to address accessibility concerns. To make video content accessible to the blind, deaf, and those with other physical or cognitive disabilities, authors are expected to provide alternative media streams and/or to embed accessibility aids (such as caption or subtitle tracks, audio description tracks, or sign-language overlays) into their media streams.

The video element is a media element whose media data is ostensibly video data, possibly with associated audio data.

The src, preload, autoplay, loop, and controls attributes are the attributes common to all media elements.

The poster attribute gives the address of an image file that the user agent can show while no video data is available. The attribute, if present, must contain a valid URL. If the specified resource is to be used, then, when the element is created or when the poster attribute is set, its value must be resolved relative to the element, and if that is successful, the resulting absolute URL must be fetched, from the element's Document's origin; this must delay the load event of the element's document. The poster frame is then the image obtained from that resource, if any.

The image given by the poster attribute, the poster frame, is intended to be a representative frame of the video (typically one of the first non-blank frames) that gives the user an idea of what the video is like.

The poster IDL attribute must reflect the poster content attribute.

When no video data is available (the element's readyState attribute is either HAVE_NOTHING, or HAVE_METADATA but no video data has yet been obtained at all), the video element represents either the poster frame, or nothing.

When a video element is paused and the current playback position is the first frame of video, the element represents either the frame of video corresponding to the current playback position or the poster frame, at the discretion of the user agent.

Notwithstanding the above, the poster frame should be preferred over nothing, but the poster frame should not be shown again after a frame of video has been shown.

When a video element is paused at any other position, the element represents the frame of video corresponding to the current playback position, or, if that is not yet available (e.g. because the video is seeking or buffering), the last frame of the video to have been rendered.

When a video element is potentially playing, it represents the frame of video at the continuously increasing "current" position. When the current playback position changes such that the last frame rendered is no longer the frame corresponding to the current playback position in the video, the new frame must be rendered. Similarly, any audio associated with the video must, if played, be played synchronized with the current playback position, at the specified volume with the specified mute state.

When a video element is neither potentially playing nor paused (e.g. when seeking or stalled), the element represents the last frame of the video to have been rendered.

Which frame in a video stream corresponds to a particular playback position is defined by the video stream's format.

In addition to the above, the user agent may provide messages to the user (such as "buffering", "no video loaded", "error", or more detailed information) by overlaying text or icons on the video or other areas of the element's playback area, or in another appropriate manner.

User agents that cannot render the video may instead make the element represent a link to an external video playback utility or to the video data itself.

video . videoWidth
video . videoHeight: These attributes return the intrinsic dimensions of the video, or zero if the dimensions are not known.

The intrinsic width and intrinsic height of the media resource are the dimensions of the resource in CSS pixels after taking into account the resource's dimensions, aspect ratio, clean aperture, resolution, and so forth, as defined for the format used by the resource. If an anamorphic format does not define how to apply the aspect ratio to the video data's dimensions to obtain the "correct" dimensions, then the user agent must apply the ratio by increasing one dimension and leaving the other unchanged.

The videoWidth IDL attribute must return the intrinsic width of the video in CSS pixels. The videoHeight IDL attribute must return the intrinsic height of the video in CSS pixels. If the element's readyState attribute is HAVE_NOTHING, then the attributes must return 0.

The video element supports dimension attributes.

Video content should be rendered inside the element's playback area such that the video content is shown centered in the playback area at the largest possible size that fits completely within it, with the video content's aspect ratio being preserved. Thus, if the aspect ratio of the playback area does not match the aspect ratio of the video, the video will be shown letterboxed or pillarboxed. Areas of the element's playback area that do not contain the video represent nothing.

The intrinsic width of a video element's playback area is the intrinsic width of the video resource, if that is available; otherwise it is the intrinsic width of the poster frame, if that is available; otherwise it is 300 CSS pixels.

The intrinsic height of a video element's playback area is the intrinsic height of the video resource, if that is available; otherwise it is the intrinsic height of the poster frame, if that is available; otherwise it is 150 CSS pixels.

User agents should provide controls to enable or disable the display of closed captions, audio description tracks, and other additional data associated with the video stream, though such features should, again, not interfere with the page's normal rendering.

User agents may allow users to view the video content in manners more suitable to the user (e.g. full-screen or in an independent resizable window). As for the other user interface features, controls to enable this should not interfere with the page's normal rendering unless the user agent is exposing a user interface. In such an independent context, however, user agents may make full user interfaces visible, with, e.g., play, pause, seeking, and volume controls, even if the controls attribute is absent.

User agents may allow video playback to affect system features that could interfere with the user's experience; for example, user agents could disable screensavers while video playback is in progress.

User agents should not provide a public API to cause videos to be shown full-screen. A script, combined with a carefully crafted video file, could trick the user into thinking a system-modal dialog had been shown, and prompt the user for a password. There is also the danger of "mere" annoyance, with pages launching full-screen videos when links are clicked or pages navigated. Instead, user-agent-specific interface features may be provided to easily allow the user to obtain a full-screen playback mode.

This example shows how to detect when a video has failed to play correctly:

<script>
 function failed(e) {
   // video playback failed - show a message saying why
   switch (e.target.error.code) {
     case e.target.error.MEDIA_ERR_ABORTED:
       alert('You aborted the video playback.');
       break;
     case e.target.error.MEDIA_ERR_NETWORK:
       alert('A network error caused the video download to fail part-way.');
       break;
     case e.target.error.MEDIA_ERR_DECODE:
       alert('The video playback was aborted due to a corruption problem or because the video used features your browser did not support.');
       break;
     case e.target.error.MEDIA_ERR_SRC_NOT_SUPPORTED:
       alert('The video could not be loaded, either because the server or network failed or because the format is not supported.');
       break;
     default:
       alert('An unknown error occurred.');
       break;
   }
 }
</script>
<p><video src="tgif.vid" autoplay controls onerror="failed(event)"></video></p>
<p><a href="tgif.vid">Download the video file</a>.</p>

4.8.7 The `audio` element

Status: Last call for comments

Categories

If the element has a controls attribute: Interactive content.

Contexts in which this element may be used:

Where embedded content is expected.

Content model:

If the element has a src attribute: transparent, but with no media element descendants.

If the element does not have a src attribute: one or more source elements, then, transparent, but with no media element descendants.

Content attributes:

src

preload

autoplay

loop

controls

DOM interface:

[NamedConstructor=Audio(),
 NamedConstructor=Audio(in DOMString src)]
interface HTMLAudioElement : HTMLMediaElement {};

An audio element represents a sound or audio stream.

Content may be provided inside the audio element. User agents should not show this content to the user; it is intended for older Web browsers which do not support audio, so that legacy audio plugins can be tried, or to show text to the users of these older browsers informing them of how to access the audio contents.

In particular, this content is not intended to address accessibility concerns. To make audio content accessible to the deaf or to those with other physical or cognitive disabilities, authors are expected to provide alternative media streams and/or to embed accessibility aids (such as transcriptions) into their media streams.

The audio element is a media element whose media data is ostensibly audio data.

The src, preload, autoplay, loop, and controls attributes are the attributes common to all media elements.

When an audio element is potentially playing, it must have its audio data played synchronized with the current playback position, at the specified volume with the specified mute state.

When an audio element is not potentially playing, audio must not play for the element.

audio = new Audio( [ url ] ): Returns a new audio element, with the src attribute set to the value passed in the argument, if applicable.

Two constructors are provided for creating HTMLAudioElement objects (in addition to the factory methods from DOM Core such as createElement()): Audio() and Audio(src). When invoked as constructors, these must return a new HTMLAudioElement object (a new audio element). The element must have its preload attribute set to the literal value "auto". If the src argument is present, the object created must have its src content attribute set to the provided value, and the user agent must invoke the object's resource selection algorithm before returning. The element's document must be the active document of the browsing context of the Window object on which the interface object of the invoked constructor is found.

4.8.8 The `source` element

Status: Last call for comments

Categories

None.

Contexts in which this element may be used:

As a child of a media element, before any flow content.

Content model:

Empty.

Content attributes:

src

type

media

DOM interface:

interface HTMLSourceElement : HTMLElement {
           attribute DOMString src;
           attribute DOMString type;
           attribute DOMString media;
};

The source element allows authors to specify multiple alternative media resources for media elements. It does not represent anything on its own.

The src attribute gives the address of the media resource. The value must be a valid URL. This attribute must be present.

The type attribute gives the type of the media resource, to help the user agent determine if it can play this media resource before fetching it. If specified, its value must be a valid MIME type. The codecs parameter may be specified and might be necessary to specify exactly how the resource is encoded. [RFC4281]

The following list shows some examples of how to use the codecs= MIME parameter in the type attribute.

H.264 Simple baseline profile video (main and extended video compatible) level 3 and Low-Complexity AAC audio in MP4 container

<source src='video.mp4' type='video/mp4; codecs="avc1.42E01E, mp4a.40.2"'>

H.264 Extended profile video (baseline-compatible) level 3 and Low-Complexity AAC audio in MP4 container

<source src='video.mp4' type='video/mp4; codecs="avc1.58A01E, mp4a.40.2"'>

H.264 Main profile video level 3 and Low-Complexity AAC audio in MP4 container

<source src='video.mp4' type='video/mp4; codecs="avc1.4D401E, mp4a.40.2"'>

H.264 'High' profile video (incompatible with main, baseline, or extended profiles) level 3 and Low-Complexity AAC audio in MP4 container

<source src='video.mp4' type='video/mp4; codecs="avc1.64001E, mp4a.40.2"'>

MPEG-4 Visual Simple Profile Level 0 video and Low-Complexity AAC audio in MP4 container

<source src='video.mp4' type='video/mp4; codecs="mp4v.20.8, mp4a.40.2"'>

MPEG-4 Advanced Simple Profile Level 0 video and Low-Complexity AAC audio in MP4 container

<source src='video.mp4' type='video/mp4; codecs="mp4v.20.240, mp4a.40.2"'>

MPEG-4 Visual Simple Profile Level 0 video and AMR audio in 3GPP container

<source src='video.3gp' type='video/3gpp; codecs="mp4v.20.8, samr"'>

Theora video and Vorbis audio in Ogg container

<source src='video.ogv' type='video/ogg; codecs="theora, vorbis"'>

Theora video and Speex audio in Ogg container

<source src='video.ogv' type='video/ogg; codecs="theora, speex"'>

Vorbis audio alone in Ogg container

<source src='audio.ogg' type='audio/ogg; codecs=vorbis'>

Speex audio alone in Ogg container

<source src='audio.spx' type='audio/ogg; codecs=speex'>

FLAC audio alone in Ogg container

<source src='audio.oga' type='audio/ogg; codecs=flac'>

Dirac video and Vorbis audio in Ogg container

<source src='video.ogv' type='video/ogg; codecs="dirac, vorbis"'>

Theora video and Vorbis audio in Matroska container

<source src='video.mkv' type='video/x-matroska; codecs="theora, vorbis"'>

The media attribute gives the intended media type of the media resource, to help the user agent determine if this media resource is useful to the user before fetching it. Its value must be a valid media query.

The default, if the media attribute is omitted, is "all", meaning that by default the media resource is suitable for all media.

If a source element is inserted as a child of a media element that has no src attribute and whose networkState has the value NETWORK_EMPTY, the user agent must invoke the media element's resource selection algorithm.

The IDL attributes src, type, and media must reflect the respective content attributes of the same name.

If the author isn't sure if the user agents will all be able to render the media resources provided, the author can listen to the error event on the last source element and trigger fallback behaviour:

<video controls autoplay>
 <source src='video.mp4' type='video/mp4; codecs="avc1.42E01E, mp4a.40.2"'>
 <source src='video.ogv' type='video/ogg; codecs="theora, vorbis"'
         onerror="fallback(parentNode)">
 ...
</video>
<script>
 function fallback(video) {
   // replace <video> with its contents
   while (video.hasChildNodes())
     video.parentNode.insertBefore(video.firstChild, video);
   video.parentNode.removeChild(video);
 }
</script>

4.8.9 Media elements

Status: Last call for comments

Media elements implement the following interface:

interface HTMLMediaElement : HTMLElement {

  // error state
  readonly attribute MediaError error;

  // network state
           attribute DOMString src;
  readonly attribute DOMString currentSrc;
  const unsigned short NETWORK_EMPTY = 0;
  const unsigned short NETWORK_IDLE = 1;
  const unsigned short NETWORK_LOADING = 2;
  const unsigned short NETWORK_NO_SOURCE = 3;
  readonly attribute unsigned short networkState;
           attribute DOMString preload;
  readonly attribute TimeRanges buffered;
  void load();
  DOMString canPlayType(in DOMString type);

  // ready state
  const unsigned short HAVE_NOTHING = 0;
  const unsigned short HAVE_METADATA = 1;
  const unsigned short HAVE_CURRENT_DATA = 2;
  const unsigned short HAVE_FUTURE_DATA = 3;
  const unsigned short HAVE_ENOUGH_DATA = 4;
  readonly attribute unsigned short readyState;
  readonly attribute boolean seeking;

  // playback state
           attribute float currentTime;
  readonly attribute float startTime;
  readonly attribute float duration;
  readonly attribute boolean paused;
           attribute float defaultPlaybackRate;
           attribute float playbackRate;
  readonly attribute TimeRanges played;
  readonly attribute TimeRanges seekable;
  readonly attribute boolean ended;
           attribute boolean autoplay;
           attribute boolean loop;
  void play();
  void pause();

  // controls
           attribute boolean controls;
           attribute float volume;
           attribute boolean muted;
};

The media element attributes, src, preload, autoplay, loop, and controls, apply to all media elements. They are defined in this section.

Media elements are used to present audio data, or video and audio data, to the user. This is referred to as media data in this section, since this section applies equally to media elements for audio or for video. The term media resource is used to refer to the complete set of media data, e.g. the complete video file, or complete audio file.

Except where otherwise specified, the task source for all the tasks queued in this section and its subsections is the media element event task source.

4.8.9.1 Error codes

Status: Last call for comments

media . error

Returns a MediaError object representing the current error state of the element.

Returns null if there is no error.

All media elements have an associated error status, which records the last error the element encountered since its resource selection algorithm was last invoked. The error attribute, on getting, must return the MediaError object created for this last error, or null if there has not been an error.

interface MediaError {
  const unsigned short MEDIA_ERR_ABORTED = 1;
  const unsigned short MEDIA_ERR_NETWORK = 2;
  const unsigned short MEDIA_ERR_DECODE = 3;
  const unsigned short MEDIA_ERR_SRC_NOT_SUPPORTED = 4;
  readonly attribute unsigned short code;
};

media . error . code: Returns the current error's error code, from the list below.

The code attribute of a MediaError object must return the code for the error, which must be one of the following:

MEDIA_ERR_ABORTED (numeric value 1): The fetching process for the media resource was aborted by the user agent at the user's request.
MEDIA_ERR_NETWORK (numeric value 2): A network error of some description caused the user agent to stop fetching the media resource, after the resource was established to be usable.
MEDIA_ERR_DECODE (numeric value 3): An error of some description occurred while decoding the media resource, after the resource was established to be usable.
MEDIA_ERR_SRC_NOT_SUPPORTED (numeric value 4): The media resource indicated by the src attribute was not suitable.

4.8.9.2 Location of the media resource

Status: Last call for comments

The src content attribute on media elements gives the address of the media resource (video, audio) to show. The attribute, if present, must contain a valid URL.

If a src attribute of a media element is set or changed, the user agent must invoke the media element's media element load algorithm. (Removing the src attribute does not do this, even if there are source elements present.)

The src IDL attribute on media elements must reflect the content attribute of the same name.

media . currentSrc

Returns the address of the current media resource.

Returns the empty string when there is no media resource.

The currentSrc IDL attribute is initially the empty string. Its value is changed by the resource selection algorithm defined below.

There are two ways to specify a media resource, the src attribute, or source elements. The attribute overrides the elements.

4.8.9.3 MIME types

Status: Last call for comments

A media resource can be described in terms of its type, specifically a MIME type, optionally with a codecs parameter. [RFC4281]

Types are usually somewhat incomplete descriptions; for example "video/mpeg" doesn't say anything except what the container type is, and even a type like "video/mp4; codecs="avc1.42E01E, mp4a.40.2"" doesn't include information like the actual bitrate (only the maximum bitrate). Thus, given a type, a user agent can often only know whether it might be able to play media of that type (with varying levels of confidence), or whether it definitely cannot play media of that type.

A type that the user agent knows it cannot render is one that describes a resource that the user agent definitely does not support, for example because it doesn't recognize the container type, or it doesn't support the listed codecs.

The MIME type "application/octet-stream" with no parameters is never a type that the user agent knows it cannot render. User agents must treat that type as equivalent to the lack of any explicit Content-Type metadata when it is used to label a potential media resource.

In the absence of a specification to the contrary, the MIME type "application/octet-stream" when used with parameters, e.g. "application/octet-stream;codecs=theora", is a type that the user agent knows it cannot render.

media . canPlayType(type): Returns the empty string (a negative response), "maybe", or "probably" based on how confident the user agent is that it can play media resources of the given type.

The canPlayType(type) method must return the empty string if type is a type that the user agent knows it cannot render; it must return "probably" if the user agent is confident that the type represents a media resource that it can render if used in with this audio or video element; and it must return "maybe" otherwise. Implementors are encouraged to return "maybe" unless the type can be confidently established as being supported or not. Generally, a user agent should never return "probably" if the type doesn't have a codecs parameter.

This script tests to see if the user agent supports a (fictional) new format to dynamically decide whether to use a video element or a plugin:

<section id="video">
 <p><a href="playing-cats.nfv">Download video</a></p>
</section>
<script>
 var videoSection = document.getElementById('video');
 var videoElement = document.createElement('video');
 var support = videoElement.canPlayType('video/x-new-fictional-format;codecs="kittens,bunnies"');
 if (support != "probably" && "New Fictional Video Plug-in" in navigator.plugins) {
   // not confident of browser support
   // but we have a plugin
   // so use plugin instead
   videoElement = document.createElement("embed");
 } else if (support == "") {
   // no support from browser and no plugin
   // do nothing
   videoElement = null;
 }
 if (videoElement) {
   while (videoSection.hasChildNodes())
     videoSection.removeChild(videoSection.firstChild);
   videoElement.setAttribute("src", "playing-cats.nfv");
   videoSection.appendChild(videoElement);
 }
</script>

The type attribute of the source element allows the user agent to avoid downloading resources that use formats it cannot render.

4.8.9.4 Network states

Status: Last call for comments

media . networkState: Returns the current state of network activity for the element, from the codes in the list below.

As media elements interact with the network, their current network activity is represented by the networkState attribute. On getting, it must return the current network state of the element, which must be one of the following values:

NETWORK_EMPTY (numeric value 0): The element has not yet been initialized. All attributes are in their initial states.
NETWORK_IDLE (numeric value 1): The element's resource selection algorithm is active and has selected a resource, but it is not actually using the network at this time.
NETWORK_LOADING (numeric value 2): The user agent is actively trying to download data.
NETWORK_NO_SOURCE (numeric value 3): The element's resource selection algorithm is active, but it has failed to find a resource to use.

The resource selection algorithm defined below describes exactly when the networkState attribute changes value and what events fire to indicate changes in this state.

4.8.9.5 Loading the media resource

Status: Last call for comments

media . load(): Causes the element to reset and start selecting and loading a new media resource from scratch.

All media elements have an autoplaying flag, which must begin in the true state, and a delaying-the-load-event flag, which must begin in the false state. While the delaying-the-load-event flag is true, the element must delay the load event of its document.

When the load() method on a media element is invoked, the user agent must run the media element load algorithm.

The media element load algorithm consists of the following steps.

Abort any already-running instance of the resource selection algorithm for this element.
If there are any tasks from the media element's media element event task source in one of the task queues, then remove those tasks.

Basically, pending events and callbacks for the media element are discarded when the media element starts loading a new resource.
If the media element's networkState is set to NETWORK_LOADING or NETWORK_IDLE, queue a task to fire a simple event named abort at the media element.
If the media element's networkState is not set to NETWORK_EMPTY, then run these substeps:
1. If a fetching process is in progress for the media element, the user agent should stop it.
2. Set the networkState attribute to NETWORK_EMPTY.
3. If readyState is not set to HAVE_NOTHING, then set it to that state.
4. If the paused attribute is false, then set to true.
5. If seeking is true, set it to false.
6. Set the current playback position to 0.
7. Queue a task to fire a simple event named emptied at the media element.
Set the playbackRate attribute to the value of the defaultPlaybackRate attribute.
Set the error attribute to null and the autoplaying flag to true.
Invoke the media element's resource selection algorithm.
Playback of any previously playing media resource for this element stops.

The resource selection algorithm for a media element is as follows. This algorithm is always invoked synchronously, but one of the first steps in the algorithm is to return and continue running the remaining steps asynchronously, meaning that it runs in the background with scripts and other tasks running in parallel. In addition, this algorithm interacts closely with the event loop mechanism; in particular, it has synchronous sections (which are triggered as part of the event loop algorithm). Steps in such sections are marked with ⌛.

Set the networkState to NETWORK_NO_SOURCE.
Asynchronously await a stable state, allowing the task that invoked this algorithm to continue. The synchronous section consists of all the remaining steps of this algorithm until the algorithm says the synchronous section has ended. (Steps in synchronous sections are marked with ⌛.)
⌛ If the media element has a src attribute, then let mode be attribute.

⌛ Otherwise, if the media element does not have a src attribute but has a source element child, then let mode be children and let candidate be the first such source element child in tree order.

⌛ Otherwise the media element has neither a src attribute nor a source element child: set the networkState to NETWORK_EMPTY, and abort these steps; the synchronous section ends.
⌛ Set the media element's delaying-the-load-event flag to true (this delays the load event), and set its networkState to NETWORK_LOADING.
⌛ Queue a task to fire a simple event named loadstart at the media element.
If mode is attribute, then run these substeps:
1. ⌛ Let absolute URL be the absolute URL that would have resulted from resolving the URL specified by the src attribute's value relative to the media element when the src attribute was last changed.
2. ⌛ If absolute URL was obtained successfully, set the currentSrc attribute to absolute URL.
3. End the synchronous section, continuing the remaining steps asynchronously.
4. If absolute URL was obtained successfully, run the resource fetch algorithm with absolute URL. If that algorithm returns without aborting this one, then the load failed.
5. Reaching this step indicates that the media resource failed to load or that the given URL could not be resolved. Set the error attribute to a new MediaError object whose code attribute is set to MEDIA_ERR_SRC_NOT_SUPPORTED.
6. Set the element's networkState attribute to the NETWORK_NO_SOURCE value.
7. Queue a task to fire a simple event named error at the media element.
8. Set the element's delaying-the-load-event flag to false. This stops delaying the load event.
9. Abort these steps. Until the load() method is invoked or the src attribute is changed, the element won't attempt to load another resource.
Otherwise, the source elements will be used; run these substeps:
1. ⌛ Let pointer be a position defined by two adjacent nodes in the media element's child list, treating the start of the list (before the first child in the list, if any) and end of the list (after the last child in the list, if any) as nodes in their own right. One node is the node before pointer, and the other node is the node after pointer. Initially, let pointer be the position between the candidate node and the next node, if there are any, or the end of the list, if it is the last node.
  
  As nodes are inserted and removed into the media element, pointer must be updated as follows:
  
  If a new node is inserted between the two nodes that define pointer
  
  Let pointer be the point between the node before pointer and the new node. In other words, insertions at pointer go after pointer.
  
  If the node before pointer is removed
  
  Let pointer be the point between the node after pointer and the node before the node after pointer. In other words, pointer doesn't move relative to the remaining nodes.
  
  If the node after pointer is removed
  
  Let pointer be the point between the node before pointer and the node after the node before pointer. Just as with the previous case, pointer doesn't move relative to the remaining nodes.
  
  Other changes don't affect pointer.
2. ⌛ Process candidate: If candidate does not have a src attribute, then end the synchronous section, and jump down to the failed step below.
3. ⌛ Let absolute URL be the absolute URL that would have resulted from resolving the URL specified by candidate's src attribute's value relative to the candidate when the src attribute was last changed.
4. ⌛ If absolute URL was not obtained successfully, then end the synchronous section, and jump down to the failed step below.
5. ⌛ If candidate has a type attribute whose value, when parsed as a MIME type (including any codecs described by the codecs parameter), represents a type that the user agent knows it cannot render, then end the synchronous section, and jump down to the failed step below.
6. ⌛ If candidate has a media attribute whose value does not match the environment of the default view, then end the synchronous section, and jump down to the failed step below.
7. ⌛ Set the currentSrc attribute to absolute URL.
8. End the synchronous section, continuing the remaining steps asynchronously.
9. Run the resource fetch algorithm with absolute URL. If that algorithm returns without aborting this one, then the load failed.
10. Failed: Queue a task to fire a simple event named error at the candidate element, in the context of the fetching process that was used to try to obtain candidate's corresponding media resource in the resource fetch algorithm.
11. Asynchronously await a stable state. The synchronous section consists of all the remaining steps of this algorithm until the algorithm says the synchronous section has ended. (Steps in synchronous sections are marked with ⌛.)
12. ⌛ Find next candidate: Let candidate be null.
13. ⌛ Search loop: If the node after pointer is the end of the list, then jump to the waiting step below.
14. ⌛ If the node after pointer is a source element, let candidate be that element.
15. ⌛ Advance pointer so that the node before pointer is now the node that was after pointer, and the node after pointer is the node after the node that used to be after pointer, if any.
16. ⌛ If candidate is null, jump back to the search loop step. Otherwise, jump back to the process candidate step.
17. ⌛ Waiting: Set the element's networkState attribute to the NETWORK_NO_SOURCE value.
18. ⌛ Set the element's delaying-the-load-event flag to false. This stops delaying the load event.
19. End the synchronous section, continuing the remaining steps asynchronously.
20. Wait until the node after pointer is a node other than the end of the list. (This step might wait forever.)
21. Asynchronously await a stable state. The synchronous section consists of all the remaining steps of this algorithm until the algorithm says the synchronous section has ended. (Steps in synchronous sections are marked with ⌛.)
22. ⌛ Set the element's delaying-the-load-event flag back to true (this delays the load event again, in case it hasn't been fired yet).
23. ⌛ Set the networkState back to NETWORK_LOADING.
24. ⌛ Jump back to the find next candidate step above.

The resource fetch algorithm for a media element and a given absolute URL is as follows:

Let the current media resource be the resource given by the absolute URL passed to this algorithm. This is now the element's media resource.
Begin to fetch the current media resource, from the media element's Document's origin.

Every 350ms (±200ms) or for every byte received, whichever is least frequent, queue a task to fire a simple event named progress at the element.

If at any point the user agent has received no data for more than about three seconds, then queue a task to fire a simple event named stalled at the element.

User agents may allow users to selectively block or slow media data downloads. When a media element's download has been blocked altogether, the user agent must act as if it was stalled (as opposed to acting as if the connection was closed). The rate of the download may also be throttled automatically by the user agent, e.g. to balance the download with other connections sharing the same bandwidth.

User agents may decide to not download more content at any time, e.g. after buffering five minutes of a one hour media resource, while waiting for the user to decide whether to play the resource or not, or while waiting for user input in an interactive resource. When a media element's download has been suspended, the user agent must set the networkState to NETWORK_IDLE and queue a task to fire a simple event named suspend at the element. If and when downloading of the resource resumes, the user agent must set the networkState to NETWORK_LOADING.

The preload attribute provides a hint regarding how much buffering the author thinks is advisable, even in the absence of the autoplay attribute.

When a user agent decides to completely stall a download, e.g. if it is waiting until the user starts playback before downloading any further content, the element's delaying-the-load-event flag must be set to false. This stops delaying the load event.

The user agent may use whatever means necessary to fetch the resource (within the constraints put forward by this and other specifications); for example, reconnecting to the server in the face of network errors, using HTTP range retrieval requests, or switching to a streaming protocol. The user agent must consider a resource erroneous only if it has given up trying to fetch it.

The networking task source tasks to process the data as it is being fetched must, when appropriate, include the relevant substeps from the following list:
If the media data cannot be fetched at all, due to network errors, causing the user agent to give up trying to fetch the resource

If the media resource is found to have Content-Type metadata that, when parsed as a MIME type (including any codecs described by the codecs parameter), represents a type that the user agent knows it cannot render (even if the actual media data is in a supported format)

If the media data can be fetched but is found by inspection to be in an unsupported format, or can otherwise not be rendered at all
DNS errors, HTTP 4xx and 5xx errors (and equivalents in other protocols), and other fatal network errors that occur before the user agent has established whether the current media resource is usable, as well as the file using an unsupported container format, or using unsupported codecs for all the data, must cause the user agent to execute the following steps:
1. The user agent should cancel the fetching process.
2. Abort this subalgorithm, returning to the resource selection algorithm.
Once enough of the media data has been fetched to determine the duration of the media resource, its dimensions, and other metadata
This indicates that the resource is usable. The user agent must follow these substeps:
1. Set the current playback position to the earliest possible position.
2. Set the readyState attribute to HAVE_METADATA.
3. For video elements, set the videoWidth and videoHeight attributes.
4. Set the duration attribute to the duration of the resource.
  
  The user agent will queue a task to fire a simple event named durationchange at the element at this point.
5. Queue a task to fire a simple event named loadedmetadata at the element.
  
  Before this task is run, as part of the event loop mechanism, the rendering will have been updated to resize the video element if appropriate.
6. If either the media resource or the address of the current media resource indicate a particular start time, then seek to that time. Ignore any resulting exceptions (if the position is out of range, it is effectively ignored).
  
  For example, a fragment identifier could be used to indicate a start position.
7. Once the readyState attribute reaches HAVE_CURRENT_DATA, after the loadeddata event has been fired, set the element's delaying-the-load-event flag to false. This stops delaying the load event.
  
  A user agent that is attempting to reduce network usage while still fetching the metadata for each media resource would also stop buffering at this point, causing the networkState attribute to switch to the NETWORK_IDLE value. This is also where a user agent would stop buffering when honoring the media element's preload's Metadata state.
The user agent is required to determine the duration of the media resource and go through this step before playing.
Once the entire media resource has been fetched (but potentially before any of it has been decoded)

Queue a task to fire a simple event named progress at the media element.

If the connection is interrupted, causing the user agent to give up trying to fetch the resource
Fatal network errors that occur after the user agent has established whether the current media resource is usable must cause the user agent to execute the following steps:
1. The user agent should cancel the fetching process.
2. Set the error attribute to a new MediaError object whose code attribute is set to MEDIA_ERR_NETWORK.
3. Queue a task to fire a simple event named error at the media element.
4. Set the element's networkState attribute to the NETWORK_EMPTY value and queue a task to fire a simple event named emptied at the element.
5. Set the element's delaying-the-load-event flag to false. This stops delaying the load event.
6. Abort the overall resource selection algorithm.
If the media data is corrupted
Fatal errors in decoding the media data that occur after the user agent has established whether the current media resource is usable must cause the user agent to execute the following steps:
1. The user agent should cancel the fetching process.
2. Set the error attribute to a new MediaError object whose code attribute is set to MEDIA_ERR_DECODE.
3. Queue a task to fire a simple event named error at the media element.
4. Set the element's networkState attribute to the NETWORK_EMPTY value and queue a task to fire a simple event named emptied at the element.
5. Set the element's delaying-the-load-event flag to false. This stops delaying the load event.
6. Abort the overall resource selection algorithm.
If the media data fetching process is aborted by the user
The fetching process is aborted by the user, e.g. because the user navigated the browsing context to another page, the user agent must execute the following steps. These steps are not followed if the load() method itself is invoked while these steps are running, as the steps above handle that particular kind of abort.
1. The user agent should cancel the fetching process.
2. Set the error attribute to a new MediaError object whose code attribute is set to MEDIA_ERR_ABORTED.
3. Queue a task to fire a simple event named abort at the media element.
4. If the media element's readyState attribute has a value equal to HAVE_NOTHING, set the element's networkState attribute to the NETWORK_EMPTY value and queue a task to fire a simple event named emptied at the element. Otherwise, set the element's networkState attribute to the NETWORK_IDLE value.
5. Set the element's delaying-the-load-event flag to false. This stops delaying the load event.
6. Abort the overall resource selection algorithm.
If the media data can be fetched but has non-fatal errors or uses, in part, codecs that are unsupported, preventing the user agent from rendering the content completely correctly but not preventing playback altogether

The server returning data that is partially usable but cannot be optimally rendered must cause the user agent to render just the bits it can handle, and ignore the rest.
When the networking task source has queued the last task as part of fetching the media resource (i.e. once the download has completed), if the fetching process completes without errors, including decoding the media data, and if all of the data is available to the user agent without network access, then, the user agent must move on to the next step. This might never happen, e.g. when streaming an infinite resource such as Web radio, or if the resource is longer than the user agent's ability to cache data.

While the user agent might still need network access to obtain parts of the media resource, the user agent must remain on this step.

For example, if the user agent has discarded the first half of a video, the user agent will remain at this step even once the playback has ended, because there is always the chance the user will seek back to the start. In fact, in this situation, once playback has ended, the user agent will end up dispatching a stalled event, as described earlier.
If the user agent ever reaches this step (which can only happen if the entire resource gets loaded and kept available): abort the overall resource selection algorithm.

The preload attribute is an enumerated attribute. The following table lists the keywords and states for the attribute — the keywords in the left column map to the states in the cell in the second column on the same row as the keyword.

Keyword	State	Brief description
`none`	None	Hints to the user agent that the author either does not expect the user to need the media resource, or that the server wants to minimise unnecessary traffic.
`metadata`	Metadata	Hints to the user agent that the author either does not expect the user to need the media resource, but that fetching the resource metadata (dimensions, first frame, track list, duration, etc) is reasonable.
`auto`	Automatic	Hints to the user agent that the user agent can put the user's needs first without risk to the server, up to and including optimistically downloading the entire resource.

The empty string is also a valid keyword, and maps to the Automatic state. The attribute's missing value default is user-agent defined, though the Automatic state is suggested in high-bandwidth situations.

The preload attribute is intended to provide a hint to the user agent about what the author thinks will lead to the best user experience. The attribute may be ignored altogether, for example based on explicit user preferences or based on the available connectivity. The attribute must be ignored if the autoplay attribute is present.

The preload IDL attribute must reflect the content attribute of the same name.

The preload attribute has no effect if used in conjunction with the autoplay attribute, though including both is not an error.

media . buffered: Returns a TimeRanges object that represents the ranges of the media resource that the user agent has buffered.

The buffered attribute must return a new static normalized TimeRanges object that represents the ranges of the media resource, if any, that the user agent has buffered, at the time the attribute is evaluated. Users agents must accurately determine the ranges available, even for media streams where this can only be determined by tedious inspection.

Typically this will be a single range anchored at the zero point, but if, e.g. the user agent uses HTTP range requests in response to seeking, then there could be multiple ranges.

User agents may discard previously buffered data.

Thus, a time position included within a range of the objects return by the buffered attribute at one time can end up being not included in the range(s) of objects returned by the same attribute at later times.

4.8.9.6 Offsets into the media resource

Status: Last call for comments

media . duration

Returns the length of the media resource, in seconds.

Returns NaN if the duration isn't available.

Returns Infinity for unbounded streams.

media . currentTime [ = value ]

Returns the current playback position, in seconds.

Can be set, to seek to the given time.

Will throw an INVALID_STATE_ERR exception if there is no selected media resource. Will throw an INDEX_SIZE_ERR exception if the given time is not within the ranges to which the user agent can seek.

media . startTime

Returns the earliest possible position, in seconds. This is the time for the start of the current clip. It might not be zero if the clip's timeline is not zero-based, or if the resource is a streaming resource (in which case it gives the earliest time that the user agent is able to seek back to).

The duration attribute must return the length of the media resource, in seconds. If no media data is available, then the attributes must return the Not-a-Number (NaN) value. If the media resource is known to be unbounded (e.g. a streaming radio), then the attribute must return the positive Infinity value.

The user agent must determine the duration of the media resource before playing any part of the media data and before setting readyState to a value equal to or greater than HAVE_METADATA, even if doing so requires seeking to multiple parts of the resource.

When the length of the media resource changes (e.g. from being unknown to known, or from a previously established length to a new length) the user agent must queue a task to fire a simple event named durationchange at the media element.

If an "infinite" stream ends for some reason, then the duration would change from positive Infinity to the time of the last frame or sample in the stream, and the durationchange event would be fired. Similarly, if the user agent initially estimated the media resource's duration instead of determining it precisely, and later revises the estimate based on new information, then the duration would change and the durationchange event would be fired.

Media elements have a current playback position, which must initially be zero. The current position is a time.

The currentTime attribute must, on getting, return the current playback position, expressed in seconds. On setting, the user agent must seek to the new value (which might raise an exception).

If the media resource is a streaming resource, then the user agent might be unable to obtain certain parts of the resource after it has expired from its buffer. Similarly, some media resources might have a timeline that doesn't start at zero. The earliest possible position is the earliest position in the stream or resource that the user agent can ever obtain again.

The startTime attribute must, on getting, return the earliest possible position, expressed in seconds.

When the earliest possible position changes, then: if the current playback position is before the earliest possible position, the user agent must seek to the earliest possible position; otherwise, if the user agent has not fired a timeupdate event at the element in the past 15 to 250ms and is not still running event handlers for such an event, then the user agent must queue a task to fire a simple event named timeupdate at the element.

Because of the above requirement and the requirement in the resource fetch algorithm that kicks in when the metadata of the clip becomes known, the current playback position can never be less than the earliest possible position.

User agents must act as if the timeline of the media resource increases linearly starting from the earliest possible position, even if the underlying media data has out-of-order or even overlapping time codes.

For example, if two clips have been concatenated into one video file, but the video format exposes the original times for the two clips, the video data might expose a timeline that goes, say, 00:15..00:29 and then 00:05..00:38. However, the user agent would not expose those times; it would instead expose the times as 00:15..00:29 and 00:29..01:02, as a single video.

The loop attribute is a boolean attribute that, if specified, indicates that the media element is to seek back to the start of the media resource upon reaching the end.

The loop IDL attribute must reflect the content attribute of the same name.

4.8.9.7 The ready states

Status: Last call for comments

media . readyState: Returns a value that expresses the current state of the element with respect to rendering the current playback position, from the codes in the list below.

Media elements have a ready state, which describes to what degree they are ready to be rendered at the current playback position. The possible values are as follows; the ready state of a media element at any particular time is the greatest value describing the state of the element:

HAVE_NOTHING (numeric value 0): No information regarding the media resource is available. No data for the current playback position is available. Media elements whose networkState attribute is NETWORK_EMPTY are always in the HAVE_NOTHING state.
HAVE_METADATA (numeric value 1): Enough of the resource has been obtained that the duration of the resource is available. In the case of a video element, the dimensions of the video are also available. The API will no longer raise an exception when seeking. No media data is available for the immediate current playback position.
HAVE_CURRENT_DATA (numeric value 2): Data for the immediate current playback position is available, but either not enough data is available that the user agent could successfully advance the current playback position in the direction of playback at all without immediately reverting to the HAVE_METADATA state, or there is no more data to obtain in the direction of playback. For example, in video this corresponds to the user agent having data from the current frame, but not the next frame; and to when playback has ended.
HAVE_FUTURE_DATA (numeric value 3): Data for the immediate current playback position is available, as well as enough data for the user agent to advance the current playback position in the direction of playback at least a little without immediately reverting to the HAVE_METADATA state. For example, in video this corresponds to the user agent having data for at least the current frame and the next frame. The user agent cannot be in this state if playback has ended, as the current playback position can never advance in this case.
HAVE_ENOUGH_DATA (numeric value 4): All the conditions described for the HAVE_FUTURE_DATA state are met, and, in addition, the user agent estimates that data is being fetched at a rate where the current playback position, if it were to advance at the rate given by the defaultPlaybackRate attribute, would not overtake the available data before playback reaches the end of the media resource.

When the ready state of a media element whose networkState is not NETWORK_EMPTY changes, the user agent must follow the steps given below:

If the previous ready state was HAVE_NOTHING, and the new ready state is HAVE_METADATA

A loadedmetadata DOM event will be fired as part of the load() algorithm.

If the previous ready state was HAVE_METADATA and the new ready state is HAVE_CURRENT_DATA or greater

If this is the first time this occurs for this media element since the load() algorithm was last invoked, the user agent must queue a task to fire a simple event named loadeddata at the element.

If the new ready state is HAVE_FUTURE_DATA or HAVE_ENOUGH_DATA, then the relevant steps below must then be run also.

If the previous ready state was HAVE_FUTURE_DATA or more, and the new ready state is HAVE_CURRENT_DATA or less

A waiting DOM event can be fired, depending on the current state of playback.

If the previous ready state was HAVE_CURRENT_DATA or less, and the new ready state is HAVE_FUTURE_DATA

The user agent must queue a task to fire a simple event named canplay.

If the element is potentially playing, the user agent must queue a task to fire a simple event named playing.

If the new ready state is HAVE_ENOUGH_DATA

If the previous ready state was HAVE_CURRENT_DATA or less, the user agent must queue a task to fire a simple event named canplay, and, if the element is also potentially playing, queue a task to fire a simple event named playing.

If the autoplaying flag is true, and the paused attribute is true, and the media element has an autoplay attribute specified, then the user agent may also set the paused attribute to false, queue a task to fire a simple event named play, and queue a task to fire a simple event named playing.

User agents are not required to autoplay, and it is suggested that user agents honor user preferences on the matter. Authors are urged to use the autoplay attribute rather than using script to force the video to play, so as to allow the user to override the behavior if so desired.

In any case, the user agent must finally queue a task to fire a simple event named canplaythrough.

It is possible for the ready state of a media element to jump between these states discontinuously. For example, the state of a media element can jump straight from HAVE_METADATA to HAVE_ENOUGH_DATA without passing through the HAVE_CURRENT_DATA and HAVE_FUTURE_DATA states.

The readyState IDL attribute must, on getting, return the value described above that describes the current ready state of the media element.

The autoplay attribute is a boolean attribute. When present, the user agent (as described in the algorithm described herein) will automatically begin playback of the media resource as soon as it can do so without stopping.

Authors are urged to use the autoplay attribute rather than using script to trigger automatic playback, as this allows the user to override the automatic playback when it is not desired, e.g. when using a screen reader. Authors are also encouraged to consider not using the automatic playback behavior at all, and instead to let the user agent wait for the user to start playback explicitly.

The autoplay IDL attribute must reflect the content attribute of the same name.

4.8.9.8 Playing the media resource

Status: Last call for comments

media . paused

Returns true if playback is paused; false otherwise.

media . ended

Returns true if playback has reached the end of the media resource.

media . defaultPlaybackRate [ = value ]

Returns the default rate of playback, for when the user is not fast-forwarding or reversing through the media resource.

Can be set, to change the default rate of playback.

The default rate has no direct effect on playback, but if the user switches to a fast-forward mode, when they return to the normal playback mode, it is expected that the rate of playback will be returned to the default rate of playback.

media . playbackRate [ = value ]

Returns the current rate playback, where 1.0 is normal speed.

Can be set, to change the rate of playback.

media . played

Returns a TimeRanges object that represents the ranges of the media resource that the user agent has played.

media . play()

Sets the paused attribute to false, loading the media resource and beginning playback if necessary. If the playback had ended, will restart it from the start.

media . pause()

Sets the paused attribute to true, loading the media resource if necessary.

The paused attribute represents whether the media element is paused or not. The attribute must initially be true.

A media element is said to be potentially playing when its paused attribute is false, the readyState attribute is either HAVE_FUTURE_DATA or HAVE_ENOUGH_DATA, the element has not ended playback, playback has not stopped due to errors, and the element has not paused for user interaction.

A media element is said to have ended playback when the element's readyState attribute is HAVE_METADATA or greater, and either the current playback position is the end of the media resource and the direction of playback is forwards and the media element does not have a loop attribute specified, or the current playback position is the earliest possible position and the direction of playback is backwards.

The ended attribute must return true if the media element has ended playback and the direction of playback is forwards, and false otherwise.

A media element is said to have stopped due to errors when the element's readyState attribute is HAVE_METADATA or greater, and the user agent encounters a non-fatal error during the processing of the media data, and due to that error, is not able to play the content at the current playback position.

A media element is said to have paused for user interaction when its paused attribute is false, the readyState attribute is either HAVE_FUTURE_DATA or HAVE_ENOUGH_DATA and the user agent has reached a point in the media resource where the user has to make a selection for the resource to continue.

It is possible for a media element to have both ended playback and paused for user interaction at the same time.

When a media element that is potentially playing stops playing because it has paused for user interaction, the user agent must queue a task to fire a simple event named timeupdate at the element.

When a media element that is potentially playing stops playing because its readyState attribute changes to a value lower than HAVE_FUTURE_DATA, without the element having ended playback, or playback having stopped due to errors, or playback having paused for user interaction, or the seeking algorithm being invoked, the user agent must queue a task to fire a simple event named timeupdate at the element, and queue a task to fire a simple event named waiting at the element.

When the current playback position reaches the end of the media resource when the direction of playback is forwards, then the user agent must follow these steps:

If the media element has a loop attribute specified, then seek to the earliest possible position of the media resource and abort these steps.
Stop playback.
The ended attribute becomes true.
The user agent must queue a task to fire a simple event named timeupdate at the element.
The user agent must queue a task to fire a simple event named ended at the element.

When the current playback position reaches the earliest possible position of the media resource when the direction of playback is backwards, then the user agent must follow these steps:

Stop playback.
The user agent must queue a task to fire a simple event named timeupdate at the element.

The defaultPlaybackRate attribute gives the desired speed at which the media resource is to play, as a multiple of its intrinsic speed. The attribute is mutable: on getting it must return the last value it was set to, or 1.0 if it hasn't yet been set; on setting the attribute must be set to the new value.

The playbackRate attribute gives the speed at which the media resource plays, as a multiple of its intrinsic speed. If it is not equal to the defaultPlaybackRate, then the implication is that the user is using a feature such as fast forward or slow motion playback. The attribute is mutable: on getting it must return the last value it was set to, or 1.0 if it hasn't yet been set; on setting the attribute must be set to the new value, and the playback must change speed (if the element is potentially playing).

If the playbackRate is positive or zero, then the direction of playback is forwards. Otherwise, it is backwards.

The "play" function in a user agent's interface must set the playbackRate attribute to the value of the defaultPlaybackRate attribute before invoking the play() method's steps. Features such as fast-forward or rewind must be implemented by only changing the playbackRate attribute.

When the defaultPlaybackRate or playbackRate attributes change value (either by being set by script or by being changed directly by the user agent, e.g. in response to user control) the user agent must queue a task to fire a simple event named ratechange at the media element.

The played attribute must return a new static normalized TimeRanges object that represents the ranges of the media resource, if any, that the user agent has so far rendered, at the time the attribute is evaluated.

When the play() method on a media element is invoked, the user agent must run the following steps.

If the media element's networkState attribute has the value NETWORK_EMPTY, invoke the media element's resource selection algorithm.
If the playback has ended and the direction of playback is forwards, seek to the earliest possible position of the media resource.

This will cause the user agent to queue a task to fire a simple event named timeupdate at the media element.
If the media element's paused attribute is true, run the following substeps:
1. Change the value of paused to false.
2. Queue a task to fire a simple event named play at the element.
3. If the media element's readyState attribute has the value HAVE_NOTHING, HAVE_METADATA, or HAVE_CURRENT_DATA, queue a task to fire a simple event named waiting at the element.
4. Otherwise, the media element's readyState attribute has the value HAVE_FUTURE_DATA or HAVE_ENOUGH_DATA; queue a task to fire a simple event named playing at the element.
Set the media element's autoplaying flag to false.

When the pause() method is invoked, the user agent must run the following steps:

If the media element's networkState attribute has the value NETWORK_EMPTY, invoke the media element's resource selection algorithm.
Set the media element's autoplaying flag to false.
If the media element's paused attribute is false, run the following steps:
1. Change the value of paused to true.
2. Queue a task to fire a simple event named timeupdate at the element.
3. Queue a task to fire a simple event named pause at the element.

When a media element is potentially playing and its Document is a fully active Document, its current playback position must increase monotonically at playbackRate units of media time per unit time of wall clock time.

This specification doesn't define how the user agent achieves the appropriate playback rate — depending on the protocol and media available, it is plausible that the user agent could negotiate with the server to have the server provide the media data at the appropriate rate, so that (except for the period between when the rate is changed and when the server updates the stream's playback rate) the client doesn't actually have to drop or interpolate any frames.

When the playbackRate is negative (playback is backwards), any corresponding audio must be muted. When the playbackRate is so low or so high that the user agent cannot play audio usefully, the corresponding audio must also be muted. If the playbackRate is not 1.0, the user agent may apply pitch adjustments to the audio as necessary to render it faithfully.

The playbackRate can be 0.0, in which case the current playback position doesn't move, despite playback not being paused (paused doesn't become true, and the pause event doesn't fire).

Media elements that are potentially playing while not in a Document must not play any video, but should play any audio component. Media elements must not stop playing just because all references to them have been removed; only once a media element to which no references exist has reached a point where no further audio remains to be played for that element (e.g. because the element is paused, or because the end of the clip has been reached, or because its playbackRate is 0.0) may the element be garbage collected.

When the current playback position of a media element changes (e.g. due to playback or seeking), the user agent must run the following steps. If the current playback position changes while the steps are running, then the user agent must wait for the steps to complete, and then must immediately rerun the steps. (These steps are thus run as often as possible or needed — if one iteration takes a long time, this can cause certain ranges to be skipped over as the user agent rushes ahead to "catch up".)

If the time was reached through the usual monotonic increase of the current playback position during normal playback, and if the user agent has not fired a timeupdate event at the element in the past 15 to 250ms and is not still running event handlers for such an event, then the user agent must queue a task to fire a simple event named timeupdate at the element. (In the other cases, such as explicit seeks, relevant events get fired as part of the overall process of changing the current playback position.)

The event thus is not to be fired faster than about 66Hz or slower than 4Hz. User agents are encouraged to vary the frequency of the event based on the system load and the average cost of processing the event each time, so that the UI updates are not any more frequent than the user agent can comfortably handle while decoding the video.

When a media element is removed from a Document, if the media element's networkState attribute has a value other than NETWORK_EMPTY then the user agent must act as if the pause() method had been invoked.

If the media element's Document stops being a fully active document, then the playback will stop until the document is active again.

4.8.9.9 Seeking

Status: Last call for comments

media . seeking: Returns true if the user agent is currently seeking.
media . seekable: Returns a TimeRanges object that represents the ranges of the media resource to which it is possible for the user agent to seek.

The seeking attribute must initially have the value false.

When the user agent is required to seek to a particular new playback position in the media resource, it means that the user agent must run the following steps:

If the media element's readyState is HAVE_NOTHING, then the user agent must raise an INVALID_STATE_ERR exception (if the seek was in response to a DOM method call or setting of an IDL attribute), and abort these steps.
If the new playback position is later than the end of the media resource, then let it be the end of the media resource instead.
If the new playback position is less than the earliest possible position, let it be that position instead.
If the (possibly now changed) new playback position is not in one of the ranges given in the seekable attribute, then the user agent must raise an INDEX_SIZE_ERR exception (if the seek was in response to a DOM method call or setting of an IDL attribute), and abort these steps.
The current playback position must be set to the given new playback position.
The seeking IDL attribute must be set to true.
The user agent must queue a task to fire a simple event named timeupdate at the element.
If the media element was potentially playing immediately before it started seeking, but seeking caused its readyState attribute to change to a value lower than HAVE_FUTURE_DATA, the user agent must queue a task to fire a simple event named waiting at the element.
If, when it reaches this step, the user agent has still not established whether or not the media data for the new playback position is available, and, if it is, decoded enough data to play back that position, the user agent must queue a task to fire a simple event named seeking at the element.
If the seek was in response to a DOM method call or setting of an IDL attribute, then continue the script. The remainder of these steps must be run asynchronously.
The user agent must wait until it has established whether or not the media data for the new playback position is available, and, if it is, until it has decoded enough data to play back that position.
The seeking IDL attribute must be set to false.
The user agent must queue a task to fire a simple event named seeked at the element.

The seekable attribute must return a new static normalized TimeRanges object that represents the ranges of the media resource, if any, that the user agent is able to seek to, at the time the attribute is evaluated.

If the user agent can seek to anywhere in the media resource, e.g. because it a simple movie file and the user agent and the server support HTTP Range requests, then the attribute would return an object with one range, whose start is the time of the first frame (typically zero), and whose end is the same as the time of the first frame plus the duration attribute's value (which would equal the time of the last frame).

The range might be continuously changing, e.g. if the user agent is buffering a sliding window on an infinite stream. This is the behavior seen with DVRs viewing live TV, for instance.

Media resources might be internally scripted or interactive. Thus, a media element could play in a non-linear fashion. If this happens, the user agent must act as if the algorithm for seeking was used whenever the current playback position changes in a discontinuous fashion (so that the relevant events fire).

4.8.9.10 User interface

Status: Last call for comments

The controls attribute is a boolean attribute. If present, it indicates that the author has not provided a scripted controller and would like the user agent to provide its own set of controls.

If the attribute is present, or if scripting is disabled for the media element, then the user agent should expose a user interface to the user. This user interface should include features to begin playback, pause playback, seek to an arbitrary position in the content (if the content supports arbitrary seeking), change the volume, change the display of closed captions or embedded sign-language tracks, select different audio tracks or turn on audio descriptions, and show the media content in manners more suitable to the user (e.g. full-screen video or in an independent resizable window). Other controls may also be made available.

Even when the attribute is absent, however, user agents may provide controls to affect playback of the media resource (e.g. play, pause, seeking, and volume controls), but such features should not interfere with the page's normal rendering. For example, such features could be exposed in the media element's context menu.

Where possible (specifically, for starting, stopping, pausing, and unpausing playback, for muting or changing the volume of the audio, and for seeking), user interface features exposed by the user agent must be implemented in terms of the DOM API described above, so that, e.g., all the same events fire.

The controls IDL attribute must reflect the content attribute of the same name.

media . volume [ = value ]

Returns the current playback volume, as a number in the range 0.0 to 1.0, where 0.0 is the quietest and 1.0 the loudest.

Can be set, to change the volume.

Throws an INDEX_SIZE_ERR if the new value is not in the range 0.0 .. 1.0.

media . muted [ = value ]

Returns true if audio is muted, overriding the volume attribute, and false if the volume attribute is being honored.

Can be set, to change whether the audio is muted or not.

The volume attribute must return the playback volume of any audio portions of the media element, in the range 0.0 (silent) to 1.0 (loudest). Initially, the volume must be 1.0, but user agents may remember the last set value across sessions, on a per-site basis or otherwise, so the volume may start at other values. On setting, if the new value is in the range 0.0 to 1.0 inclusive, the attribute must be set to the new value and the playback volume must be correspondingly adjusted as soon as possible after setting the attribute, with 0.0 being silent, and 1.0 being the loudest setting, values in between increasing in loudness. The range need not be linear. The loudest setting may be lower than the system's loudest possible setting; for example the user could have set a maximum volume. If the new value is outside the range 0.0 to 1.0 inclusive, then, on setting, an INDEX_SIZE_ERR exception must be raised instead.

The muted attribute must return true if the audio channels are muted and false otherwise. Initially, the audio channels should not be muted (false), but user agents may remember the last set value across sessions, on a per-site basis or otherwise, so the muted state may start as muted (true). On setting, the attribute must be set to the new value; if the new value is true, audio playback for this media resource must then be muted, and if false, audio playback must then be enabled.

Whenever either the muted or volume attributes are changed, the user agent must queue a task to fire a simple event named volumechange at the media element.

4.8.9.11 Time ranges

Status: Last call for comments

Objects implementing the TimeRanges interface represent a list of ranges (periods) of time.

interface TimeRanges {
  readonly attribute unsigned long length;
  float start(in unsigned long index);
  float end(in unsigned long index);
};

media . length

Returns the number of ranges in the object.

time = media . start(index)

Returns the time for the start of the range with the given index.

Throws an INDEX_SIZE_ERR if the index is out of range.

time = media . end(index)

Returns the time for the end of the range with the given index.

Throws an INDEX_SIZE_ERR if the index is out of range.

The length IDL attribute must return the number of ranges represented by the object.

The start(index) method must return the position of the start of the indexth range represented by the object, in seconds measured from the start of the timeline that the object covers.

The end(index) method must return the position of the end of the indexth range represented by the object, in seconds measured from the start of the timeline that the object covers.

These methods must raise INDEX_SIZE_ERR exceptions if called with an index argument greater than or equal to the number of ranges represented by the object.

When a TimeRanges object is said to be a normalized TimeRanges object, the ranges it represents must obey the following criteria:

The start of a range must be greater than the end of all earlier ranges.
The start of a range must be less than the end of that same range.

In other words, the ranges in such an object are ordered, don't overlap, aren't empty, and don't touch (adjacent ranges are folded into one bigger range).

The timelines used by the objects returned by the buffered, seekable and played IDL attributes of media elements must be the same as that element's media resource's timeline.

4.8.9.12 Event summary

Status: Last call for comments

This section is non-normative.

The following events fire on media elements as part of the processing model described above:

Event name	Interface	Dispatched when...	Preconditions
`loadstart`	`Event`	The user agent begins looking for media data, as part of the resource selection algorithm.	`networkState` equals `NETWORK_LOADING`
`progress`	`Event`	The user agent is fetching media data.	`networkState` equals `NETWORK_LOADING`
`suspend`	`Event`	The user agent is intentionally not currently fetching media data, but does not have the entire media resource downloaded.	`networkState` equals `NETWORK_IDLE`
`abort`	`Event`	The user agent stops fetching the media data before it is completely downloaded, but not due to an error.	`error` is an object with the code `MEDIA_ERR_ABORTED`. `networkState` equals either `NETWORK_EMPTY` or `NETWORK_IDLE`, depending on when the download was aborted.
`error`	`Event`	An error occurs while fetching the media data.	`error` is an object with the code `MEDIA_ERR_NETWORK` or higher. `networkState` equals either `NETWORK_EMPTY` or `NETWORK_IDLE`, depending on when the download was aborted.
`emptied`	`Event`	A media element whose `networkState` was previously not in the `NETWORK_EMPTY` state has just switched to that state (either because of a fatal error during load that's about to be reported, or because the `load()` method was invoked while the resource selection algorithm was already running).	`networkState` is `NETWORK_EMPTY`; all the IDL attributes are in their initial states.
`stalled`	`Event`	The user agent is trying to fetch media data, but data is unexpectedly not forthcoming.	`networkState` is `NETWORK_LOADING`.
`play`	`Event`	Playback has begun. Fired after the `play()` method has returned.	`paused` is newly false.
`pause`	`Event`	Playback has been paused. Fired after the `pause` method has returned.	`paused` is newly true.
`loadedmetadata`	`Event`	The user agent has just determined the duration and dimensions of the media resource.	`readyState` is newly equal to `HAVE_METADATA` or greater for the first time.
`loadeddata`	`Event`	The user agent can render the media data at the current playback position for the first time.	`readyState` newly increased to `HAVE_CURRENT_DATA` or greater for the first time.
`waiting`	`Event`	Playback has stopped because the next frame is not available, but the user agent expects that frame to become available in due course.	`readyState` is newly equal to or less than `HAVE_CURRENT_DATA`, and `paused` is false. Either `seeking` is true, or the current playback position is not contained in any of the ranges in `buffered`. It is possible for playback to stop for two other reasons without `paused` being false, but those two reasons do not fire this event: maybe playback ended, or playback stopped due to errors.
`playing`	`Event`	Playback has started.	`readyState` is newly equal to or greater than `HAVE_FUTURE_DATA`, `paused` is false, `seeking` is false, or the current playback position is contained in one of the ranges in `buffered`.
`canplay`	`Event`	The user agent can resume playback of the media data, but estimates that if playback were to be started now, the media resource could not be rendered at the current playback rate up to its end without having to stop for further buffering of content.	`readyState` newly increased to `HAVE_FUTURE_DATA` or greater.
`canplaythrough`	`Event`	The user agent estimates that if playback were to be started now, the media resource could be rendered at the current playback rate all the way to its end without having to stop for further buffering.	`readyState` is newly equal to `HAVE_ENOUGH_DATA`.
`seeking`	`Event`	The `seeking` IDL attribute changed to true and the seek operation is taking long enough that the user agent has time to fire the event.
`seeked`	`Event`	The `seeking` IDL attribute changed to false.
`timeupdate`	`Event`	The current playback position changed as part of normal playback or in an especially interesting way, for example discontinuously.
`ended`	`Event`	Playback has stopped because the end of the media resource was reached.	`currentTime` equals the end of the media resource; `ended` is true.
`ratechange`	`Event`	Either the `defaultPlaybackRate` or the `playbackRate` attribute has just been updated.
`durationchange`	`Event`	The `duration` attribute has just been updated.
`volumechange`	`Event`	Either the `volume` attribute or the `muted` attribute has changed. Fired after the relevant attribute's setter has returned.

4.8.9.13 Security and privacy considerations

Status: Last call for comments

The main security and privacy implications of the video and audio elements come from the ability to embed media cross-origin. There are two directions that threats can flow: from hostile content to a victim page, and from a hostile page to victim content.

If a victim page embeds hostile content, the threat is that the content might contain scripted code that attempts to interact with the Document that embeds the content. To avoid this, user agents must ensure that there is no access from the content to the embedding page. In the case of media content that uses DOM concepts, the embedded content must be treated as if it was in its own unrelated top-level browsing context.

For instance, if an SVG animation was embedded in a video element, the user agent would not give it access to the DOM of the outer page. From the perspective of scripts in the SVG resource, the SVG file would appear to be in a lone top-level browsing context with no parent.

If a hostile page embeds victim content, the threat is that the embedding page could obtain information from the content that it would not otherwise have access to. The API does expose some information: the existence of the media, its type, its duration, its size, and the performance characteristics of its host. Such information is already potentially problematic, but in practice the same information can more or less be obtained using the img element, and so it has been deemed acceptable.

However, significantly more sensitive information could be obtained if the user agent further exposes metadata within the content such as subtitles or chapter titles. This version of the API does not expose such information. Future extensions to this API will likely reuse a mechanism such as CORS to check that the embedded content's site has opted in to exposing such information. [CORS]

An attacker could trick a user running within a corporate network into visiting a site that attempts to load a video from a previously leaked location on the corporation's intranet. If such a video included confidential plans for a new product, then being able to read the subtitles would present a confidentiality breach.

4.8.10 The `canvas` element

Status: Last call for comments. ISSUE-74 (canvas-accessibility) blocks progress to Last Call

Categories

Contexts in which this element may be used:

Where embedded content is expected.

Content model:

Transparent.

Content attributes:

width

height

DOM interface:

interface HTMLCanvasElement : HTMLElement {
           attribute unsigned long width;
           attribute unsigned long height;

  DOMString toDataURL(in optional DOMString type, in any... args);

  object getContext(in DOMString contextId);
};

The canvas element provides scripts with a resolution-dependent bitmap canvas, which can be used for rendering graphs, game graphics, or other visual images on the fly.

Authors should not use the canvas element in a document when a more suitable element is available. For example, it is inappropriate to use a canvas element to render a page heading: if the desired presentation of the heading is graphically intense, it should be marked up using appropriate elements (typically h1) and then styled using CSS and supporting technologies such as XBL.

When authors use the canvas element, they must also provide content that, when presented to the user, conveys essentially the same function or purpose as the bitmap canvas. This content may be placed as content of the canvas element. The contents of the canvas element, if any, are the element's fallback content.

In interactive visual media, if scripting is enabled for the canvas element, and if support for canvas elements has been enabled, the canvas element represents embedded content consisting of a dynamically created image.

In non-interactive, static, visual media, if the canvas element has been previously painted on (e.g. if the page was viewed in an interactive visual medium and is now being printed, or if some script that ran during the page layout process painted on the element), then the canvas element represents embedded content with the current image and size. Otherwise, the element represents its fallback content instead.

In non-visual media, and in visual media if scripting is disabled for the canvas element or if support for canvas elements has been disabled, the canvas element represents its fallback content instead.

When a canvas element represents embedded content, the user can still focus descendants of the canvas element (in the fallback content). This allows authors to make an interactive canvas keyboard-focusable: authors should have a one-to-one mapping of interactive regions to focusable elements in the fallback content.

The canvas element has two attributes to control the size of the coordinate space: width and height. These attributes, when specified, must have values that are valid non-negative integers. The rules for parsing non-negative integers must be used to obtain their numeric values. If an attribute is missing, or if parsing its value returns an error, then the default value must be used instead. The width attribute defaults to 300, and the height attribute defaults to 150.

The intrinsic dimensions of the canvas element equal the size of the coordinate space, with the numbers interpreted in CSS pixels. However, the element can be sized arbitrarily by a style sheet. During rendering, the image is scaled to fit this layout size.

The size of the coordinate space does not necessarily represent the size of the actual bitmap that the user agent will use internally or during rendering. On high-definition displays, for instance, the user agent may internally use a bitmap with two device pixels per unit in the coordinate space, so that the rendering remains at high quality throughout.

When the canvas element is created, and subsequently whenever the width and height attributes are set (whether to a new value or to the previous value), the bitmap and any associated contexts must be cleared back to their initial state and reinitialized with the newly specified coordinate space dimensions.

When the canvas is initialized, its bitmap must be cleared to transparent black.

The width and height IDL attributes must reflect the respective content attributes of the same name.

Only one square appears to be drawn in the following example:

  // canvas is a reference to a <canvas> element
  var context = canvas.getContext('2d');
  context.fillRect(0,0,50,50);
  canvas.setAttribute('width', '300'); // clears the canvas
  context.fillRect(0,100,50,50);
  canvas.width = canvas.width; // clears the canvas
  context.fillRect(100,0,50,50); // only this square remains

To draw on the canvas, authors must first obtain a reference to a context using the getContext(contextId) method of the canvas element.

context = canvas . getContext(contextId)

Returns an object that exposes an API for drawing on the canvas.

Returns null if the given context ID is not supported.

Contexts are defined by other specifications.

Vendors may also define experimental contexts using the syntax vendorname-context, for example, moz-3d.

When the UA is passed an empty string or a string specifying a context that it does not support, then it must return null. String comparisons must be case-sensitive.

url = canvas . toDataURL( [ type, ... ])

Returns a data: URL for the image in the canvas.

The first argument, if provided, controls the type of the image to be returned (e.g. PNG or JPEG). The default is image/png; that type is also used if the given type isn't supported. The other arguments are specific to the type, and control the way that the image is generated, as given in the table below.

The toDataURL() method must, when called with no arguments, return a data: URL containing a representation of the image as a PNG file. [PNG]

If the canvas has no pixels (i.e. either its horizontal dimension or its vertical dimension is zero) then the method must return the string "data:,". (This is the shortest data: URL; it represents the empty string in a text/plain resource.)

When the toDataURL(type) method is called with one or more arguments, it must return a data: URL containing a representation of the image in the format given by type. The possible values are MIME types with no parameters, for example image/png, image/jpeg, or even maybe image/svg+xml if the implementation actually keeps enough information to reliably render an SVG image from the canvas.

For image types that do not support an alpha channel, the image must be composited onto a solid black background using the source-over operator, and the resulting image must be the one used to create the data: URL.

Only support for image/png is required. User agents may support other types. If the user agent does not support the requested type, it must return the image using the PNG format.

User agents must convert the provided type to ASCII lowercase before establishing if they support that type and before creating the data: URL.

When trying to use types other than image/png, authors can check if the image was really returned in the requested format by checking to see if the returned string starts with one the exact strings "data:image/png," or "data:image/png;". If it does, the image is PNG, and thus the requested type was not supported. (The one exception to this is if the canvas has either no height or no width, in which case the result might simply be "data:,".)

If the method is invoked with the first argument giving a type corresponding to one of the types given in the first column of the following table, and the user agent supports that type, then the subsequent arguments, if any, must be treated as described in the second cell of that row.

Type	Other arguments
image/jpeg	The second argument, if it is a number between 0.0 and 1.0, must be treated as the desired quality level. If it is not a number or is outside that range, the user agent must use its default value, as if the argument had been omitted.

Other arguments must be ignored and must not cause the user agent to raise an exception. A future version of this specification will probably define other parameters to be passed to toDataURL() to allow authors to more carefully control compression settings, image metadata, etc.

4.8.10.1 Color spaces and color correction

Status: Last call for comments

The canvas APIs must perform color correction at only two points: when rendering images with their own gamma correction and color space information onto the canvas, to convert the image to the color space used by the canvas (e.g. using the 2D Context's drawImage() method with an HTMLImageElement object), and when rendering the actual canvas bitmap to the output device.

Thus, in the 2D context, colors used to draw shapes onto the canvas will exactly match colors obtained through the getImageData() method.

The toDataURL() method must not include color space information in the resource returned. Where the output format allows it, the color of pixels in resources created by toDataURL() must match those returned by the getImageData() method.

In user agents that support CSS, the color space used by a canvas element must match the color space used for processing any colors for that element in CSS.

The gamma correction and color space information of images must be handled in such a way that an image rendered directly using an img element would use the same colors as one painted on a canvas element that is then itself rendered. Furthermore, the rendering of images that have no color correction information (such as those returned by the toDataURL() method) must be rendered with no color correction.

Thus, in the 2D context, calling the drawImage() method to render the output of the toDataURL() method to the canvas, given the appropriate dimensions, has no visible effect.

4.8.10.2 Security with `canvas` elements

Status: Last call for comments

Information leakage can occur if scripts from one origin can access information (e.g. read pixels) from images from another origin (one that isn't the same).

To mitigate this, canvas elements are defined to have a flag indicating whether they are origin-clean. All canvas elements must start with their origin-clean set to true. The flag must be set to false if any of the following actions occur:

The element's 2D context's drawImage() method is called with an HTMLImageElement or an HTMLVideoElement whose origin is not the same as that of the Document object that owns the canvas element.
The element's 2D context's drawImage() method is called with an HTMLCanvasElement whose origin-clean flag is false.
The element's 2D context's fillStyle attribute is set to a CanvasPattern object that was created from an HTMLImageElement or an HTMLVideoElement whose origin was not the same as that of the Document object that owns the canvas element when the pattern was created.
The element's 2D context's fillStyle attribute is set to a CanvasPattern object that was created from an HTMLCanvasElement whose origin-clean flag was false when the pattern was created.
The element's 2D context's strokeStyle attribute is set to a CanvasPattern object that was created from an HTMLImageElement or an HTMLVideoElement whose origin was not the same as that of the Document object that owns the canvas element when the pattern was created.
The element's 2D context's strokeStyle attribute is set to a CanvasPattern object that was created from an HTMLCanvasElement whose origin-clean flag was false when the pattern was created.

Whenever the toDataURL() method of a canvas element whose origin-clean flag is set to false is called, the method must raise a SECURITY_ERR exception.

Whenever the getImageData() method of the 2D context of a canvas element whose origin-clean flag is set to false is called with otherwise correct arguments, the method must raise a SECURITY_ERR exception.

Even resetting the canvas state by changing its width or height attributes doesn't reset the origin-clean flag.

4.8.11 The `map` element

Status: Last call for comments

Categories

When the element only contains phrasing content: phrasing content.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Transparent.

Content attributes:

name

DOM interface:

interface HTMLMapElement : HTMLElement {
           attribute DOMString name;
  readonly attribute HTMLCollection areas;
  readonly attribute HTMLCollection images;
};

The map element, in conjunction with any area element descendants, defines an image map. The element represents its children.

The name attribute gives the map a name so that it can be referenced. The attribute must be present and must have a non-empty value with no space characters. The value of the name attribute must not be a compatibility-caseless match for the value of the name attribute of another map element in the same document. If the id attribute is also specified, both attributes must have the same value.

map . areas: Returns an HTMLCollection of the area elements in the map.
map . images: Returns an HTMLCollection of the img and object elements that use the map.

The areas attribute must return an HTMLCollection rooted at the map element, whose filter matches only area elements.

The images attribute must return an HTMLCollection rooted at the Document node, whose filter matches only img and object elements that are associated with this map element according to the image map processing model.

The IDL attribute name must reflect the content attribute of the same name.

4.8.12 The `area` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where phrasing content is expected, but only if there is a map element ancestor.

Content model:

Empty.

Content attributes:

alt

coords

shape

href

target

ping

rel

media

hreflang

type

DOM interface:

interface HTMLAreaElement : HTMLElement {
           attribute DOMString alt;
           attribute DOMString coords;
           attribute DOMString shape;
  stringifier attribute DOMString href;
           attribute DOMString target;
           attribute DOMString ping;
           attribute DOMString rel;
  readonly attribute DOMTokenList relList;
           attribute DOMString media;
           attribute DOMString hreflang;
           attribute DOMString type;

  // URL decomposition IDL attributes
           attribute DOMString protocol;
           attribute DOMString host;
           attribute DOMString hostname;
           attribute DOMString port;
           attribute DOMString pathname;
           attribute DOMString search;
           attribute DOMString hash;
};

The area element represents either a hyperlink with some text and a corresponding area on an image map, or a dead area on an image map.

If the area element has an href attribute, then the area element represents a hyperlink. In this case, the alt attribute must be present. It specifies the text of the hyperlink. Its value must be text that, when presented with the texts specified for the other hyperlinks of the image map, and with the alternative text of the image, but without the image itself, provides the user with the same kind of choice as the hyperlink would when used without its text but with its shape applied to the image. The alt attribute may be left blank if there is another area element in the same image map that points to the same resource and has a non-blank alt attribute.

If the area element has no href attribute, then the area represented by the element cannot be selected, and the alt attribute must be omitted.

In both cases, the shape and coords attributes specify the area.

The shape attribute is an enumerated attribute. The following table lists the keywords defined for this attribute. The states given in the first cell of the rows with keywords give the states to which those keywords map. Some of the keywords are non-conforming, as noted in the last column.

State	Keywords	Notes
Circle state	`circle`
Circle state	`circ`	Non-conforming
Default state	`default`
Polygon state	`poly`
Polygon state	`polygon`	Non-conforming
Rectangle state	`rect`
Rectangle state	`rectangle`	Non-conforming

The attribute may be omitted. The missing value default is the rectangle state.

The coords attribute must, if specified, contain a valid list of integers. This attribute gives the coordinates for the shape described by the shape attribute. The processing for this attribute is described as part of the image map processing model.

In the circle state, area elements must have a coords attribute present, with three integers, the last of which must be non-negative. The first integer must be the distance in CSS pixels from the left edge of the image to the center of the circle, the second integer must be the distance in CSS pixels from the top edge of the image to the center of the circle, and the third integer must be the radius of the circle, again in CSS pixels.

In the default state state, area elements must not have a coords attribute. (The area is the whole image.)

In the polygon state, area elements must have a coords attribute with at least six integers, and the number of integers must be even. Each pair of integers must represent a coordinate given as the distances from the left and the top of the image in CSS pixels respectively, and all the coordinates together must represent the points of the polygon, in order.

In the rectangle state, area elements must have a coords attribute with exactly four integers, the first of which must be less than the third, and the second of which must be less than the fourth. The four points must represent, respectively, the distance from the left edge of the image to the left side of the rectangle, the distance from the top edge to the top side, the distance from the left edge to the right side, and the distance from the top edge to the bottom side, all in CSS pixels.

When user agents allow users to follow hyperlinks created using the area element, as described in the next section, the href, target and ping attributes decide how the link is followed. The rel, media, hreflang, and type attributes may be used to indicate to the user the likely nature of the target resource before the user follows the link.

The target, ping, rel, media, hreflang, and type attributes must be omitted if the href attribute is not present.

The activation behavior of area elements is to run the following steps:

If the DOMActivate event in question is not trusted (i.e. a click() method call was the reason for the event being dispatched), and the area element's target attribute is such that applying the rules for choosing a browsing context given a browsing context name, using the value of the target attribute as the browsing context name, would result in there not being a chosen browsing context, then raise an INVALID_ACCESS_ERR exception and abort these steps.
Otherwise, the user agent must follow the hyperlink defined by the area element, if any.

The IDL attributes alt, coords, href, target, ping, rel, media, hreflang, and type, each must reflect the respective content attributes of the same name.

The IDL attribute shape must reflect the shape content attribute, limited to only known values.

The IDL attribute relList must reflect the rel content attribute.

The area element also supports the complement of URL decomposition IDL attributes, protocol, host, port, hostname, pathname, search, and hash. These must follow the rules given for URL decomposition IDL attributes, with the input being the result of resolving the element's href attribute relative to the element, if there is such an attribute and resolving it is successful, or the empty string otherwise; and the common setter action being the same as setting the element's href attribute to the new output value.

4.8.13 Image maps

Status: Last call for comments

4.8.13.1 Authoring

Status: Last call for comments

An image map allows geometric areas on an image to be associated with hyperlinks.

An image, in the form of an img element or an object element representing an image, may be associated with an image map (in the form of a map element) by specifying a usemap attribute on the img or object element. The usemap attribute, if specified, must be a valid hash-name reference to a map element.

Consider an image that looks as follows:

A line with four shapes in it, equally spaced: a red hollow box, a green circle, a blue triangle, and a yellow four-pointed star.

If we wanted just the colored areas to be clickable, we could do it as follows:

<p>
 Please select a shape:
 <img src="shapes.png" usemap="#shapes"
      alt="Four shapes are available: a red hollow box, a green circle, a blue triangle, and a yellow four-pointed star.">
 <map name="shapes">
  <area shape=rect coords="50,50,100,100"> <!-- the hole in the red box -->
  <area shape=rect coords="25,25,125,125" href="red.html" alt="Red box.">
  <area shape=circle coords="200,75,50" href="green.html" alt="Green circle.">
  <area shape=poly coords="325,25,262,125,388,125" href="blue.html" alt="Blue triangle.">
  <area shape=poly coords="450,25,435,60,400,75,435,90,450,125,465,90,500,75,465,60"
        href="yellow.html" alt="Yellow star.">
 </map>
</p>

4.8.13.2 Processing model

Status: Last call for comments

If an img element or an object element representing an image has a usemap attribute specified, user agents must process it as follows:

First, rules for parsing a hash-name reference to a map element must be followed. This will return either an element (the map) or null.
If that returned null, then abort these steps. The image is not associated with an image map after all.
Otherwise, the user agent must collect all the area elements that are descendants of the map. Let those be the areas.

Having obtained the list of area elements that form the image map (the areas), interactive user agents must process the list in one of two ways.

If the user agent intends to show the text that the img element represents, then it must use the following steps.

In user agents that do not support images, or that have images disabled, object elements cannot represent images, and thus this section never applies (the fallback content is shown instead). The following steps therefore only apply to img elements.

Remove all the area elements in areas that have no href attribute.
Remove all the area elements in areas that have no alt attribute, or whose alt attribute's value is the empty string, if there is another area element in areas with the same value in the href attribute and with a non-empty alt attribute.
Each remaining area element in areas represents a hyperlink. Those hyperlinks should all be made available to the user in a manner associated with the text of the img.

In this context, user agents may represent area and img elements with no specified alt attributes, or whose alt attributes are the empty string or some other non-visible text, in a user-agent-defined fashion intended to indicate the lack of suitable author-provided text.

If the user agent intends to show the image and allow interaction with the image to select hyperlinks, then the image must be associated with a set of layered shapes, taken from the area elements in areas, in reverse tree order (so the last specified area element in the map is the bottom-most shape, and the first element in the map, in tree order, is the top-most shape).

Each area element in areas must be processed as follows to obtain a shape to layer onto the image:

Find the state that the element's shape attribute represents.
Use the rules for parsing a list of integers to parse the element's coords attribute, if it is present, and let the result be the coords list. If the attribute is absent, let the coords list be the empty list.
If the number of items in the coords list is less than the minimum number given for the area element's current state, as per the following table, then the shape is empty; abort these steps.

State Minimum number of items
Circle state 3
Default state 0
Polygon state 6
Rectangle state 4
Check for excess items in the coords list as per the entry in the following list corresponding to the shape attribute's state:

Circle state

Drop any items in the list beyond the third.

Default state

Drop all items in the list.

Polygon state

Drop the last item if there's an odd number of items.

Rectangle state

Drop any items in the list beyond the fourth.
If the shape attribute represents the rectangle state, and the first number in the list is numerically less than the third number in the list, then swap those two numbers around.
If the shape attribute represents the rectangle state, and the second number in the list is numerically less than the fourth number in the list, then swap those two numbers around.
If the shape attribute represents the circle state, and the third number in the list is less than or equal to zero, then the shape is empty; abort these steps.
Now, the shape represented by the element is the one described for the entry in the list below corresponding to the state of the shape attribute:

Circle state

Let x be the first number in coords, y be the second number, and r be the third number.

The shape is a circle whose center is x CSS pixels from the left edge of the image and x CSS pixels from the top edge of the image, and whose radius is r pixels.

Default state

The shape is a rectangle that exactly covers the entire image.

Polygon state

Let x_i be the (2i)th entry in coords, and y_i be the (2i+1)th entry in coords (the first entry in coords being the one with index 0).

Let the coordinates be (x_i, y_i), interpreted in CSS pixels measured from the top left of the image, for all integer values of i from 0 to (N/2)-1, where N is the number of items in coords.

The shape is a polygon whose vertices are given by the coordinates, and whose interior is established using the even-odd rule. [GRAPHICS]

Rectangle state

Let x₁ be the first number in coords, y₁ be the second number, x₂ be the third number, and y₂ be the fourth number.

The shape is a rectangle whose top-left corner is given by the coordinate (x₁, y₁) and whose bottom right corner is given by the coordinate (x₂, y₂), those coordinates being interpreted as CSS pixels from the top left corner of the image.

For historical reasons, the coordinates must be interpreted relative to the displayed image, even if it stretched using CSS or the image element's width and height attributes.

State	Minimum number of items
Circle state	3
Default state	0
Polygon state	6
Rectangle state	4

Mouse clicks on an image associated with a set of layered shapes per the above algorithm must be dispatched to the top-most shape covering the point that the pointing device indicated (if any), and then, must be dispatched again (with a new Event object) to the image element itself. User agents may also allow individual area elements representing hyperlinks to be selected and activated (e.g. using a keyboard); events from this are not also propagated to the image.

Because a map element (and its area elements) can be associated with multiple img and object elements, it is possible for an area element to correspond to multiple focusable areas of the document.

Image maps are live; if the DOM is mutated, then the user agent must act as if it had rerun the algorithms for image maps.

4.8.14 MathML

Status: Last call for comments

The math element from the MathML namespace falls into the embedded content, phrasing content, and flow content categories for the purposes of the content models in this specification.

User agents must handle text other than inter-element whitespace found in MathML elements whose content models do not allow straight text by pretending for the purposes of MathML content models, layout, and rendering that that text is actually wrapped in an mtext element in the MathML namespace. (Such text is not, however, conforming.)

User agents must act as if any MathML element whose contents does not match the element's content model was replaced, for the purposes of MathML layout and rendering, by an merror element in the MathML namespace containing some appropriate error message.

To enable authors to use MathML tools that only accept MathML in its XML form, interactive HTML user agents are encouraged to provide a way to export any MathML fragment as an XML namespace-well-formed XML fragment.

The semantics of MathML elements are defined by the MathML specification and other relevant specifications. [MATHML]

Here is an example of the use of MathML in an HTML document:

<!DOCTYPE html>
<html>
 <head>
  <title>The quadratic formula</title>
 </head>
 <body>
  <h1>The quadratic formula</h1>
  <p>
   <math>
    <mi>x</mi>
    <mo>=</mo>
    <mfrac>
     <mrow>
      <mo form="prefix">−</mo> <mi>b</mi>
      <mo>±</mo>
      <msqrt>
       <msup> <mi>b</mi> <mn>2</mn> </msup>
       <mo>−</mo>
       <mn>4</mn> <mo>⁢</mo> <mi>a</mi> <mo>⁢</mo> <mi>c</mi>
      </msqrt>
     </mrow>
     <mrow>
      <mn>2</mn> <mo>⁢</mo> <mi>a</mi>
     </mrow>
    </mfrac>
   </math>
  </p>
 </body>
</html>

4.8.15 SVG

Status: Last call for comments

The svg element from the SVG namespace falls into the embedded content, phrasing content, and flow content categories for the purposes of the content models in this specification.

To enable authors to use SVG tools that only accept SVG in its XML form, interactive HTML user agents are encouraged to provide a way to export any SVG fragment as an XML namespace-well-formed XML fragment.

When the SVG foreignObject element contains elements from the HTML namespace, such elements must all be flow content. [SVG]

The content model for title elements in the SVG namespace inside HTML documents is phrasing content. (This further constrains the requirements given in the SVG specification.)

The semantics of SVG elements are defined by the SVG specification and other relevant specifications. [SVG]

The SVG specification includes requirements regarding the handling of elements in the DOM that are not in the SVG namespace, that are in SVG fragments, and that are not included in a foreignObject element. This specification does not define any processing for elements in SVG fragments that are not in the HTML namespace; they are considered neither conforming nor non-conforming from the perspective of this specification.

4.8.16 Dimension attributes

Status: Last call for comments

Author requirements: The width and height attributes on img, iframe, embed, object, video, and, when their type attribute is in the Image Button state, input elements may be specified to give the dimensions of the visual content of the element (the width and height respectively, relative to the nominal direction of the output medium), in CSS pixels. The attributes, if specified, must have values that are valid non-negative integers.

The specified dimensions given may differ from the dimensions specified in the resource itself, since the resource may have a resolution that differs from the CSS pixel resolution. (On screens, CSS pixels have a resolution of 96ppi, but in general the CSS pixel resolution depends on the reading distance.) If both attributes are specified, then one of the following statements must be true:

specified width - 0.5 ≤ specified height * target ratio ≤ specified width + 0.5
specified height - 0.5 ≤ specified width / target ratio ≤ specified height + 0.5
specified height = specified width = 0

The target ratio is the ratio of the intrinsic width to the intrinsic height in the resource. The specified width and specified height are the values of the width and height attributes respectively.

The two attributes must be omitted if the resource in question does not have both an intrinsic width and an intrinsic height.

If the two attributes are both zero, it indicates that the element is not intended for the user (e.g. it might be a part of a service to count page views).

The dimension attributes are not intended to be used to stretch the image.

User agent requirements: User agents are expected to use these attributes as hints for the rendering.

The width and height IDL attributes on the iframe, embed, object, and video elements must reflect the respective content attributes of the same name.

4.9 Tabular data

Status: Last call for comments. ISSUE-32 (table-summary) blocks progress to Last Call

4.9.1 The `table` element

Status: Last call for comments. ISSUE-92 (cleanuptable) blocks progress to Last Call

Categories

Contexts in which this element may be used:

Where flow content is expected.

Content model:

In this order: optionally a caption element, followed by either zero or more colgroup elements, followed optionally by a thead element, followed optionally by a tfoot element, followed by either zero or more tbody elements or one or more tr elements, followed optionally by a tfoot element (but there can only be one tfoot element child in total).

Content attributes:

summary (but see prose)

DOM interface:

interface HTMLTableElement : HTMLElement {
           attribute HTMLTableCaptionElement caption;
  HTMLElement createCaption();
  void deleteCaption();
           attribute HTMLTableSectionElement tHead;
  HTMLElement createTHead();
  void deleteTHead();
           attribute HTMLTableSectionElement tFoot;
  HTMLElement createTFoot();
  void deleteTFoot();
  readonly attribute HTMLCollection tBodies;
  HTMLElement createTBody();
  readonly attribute HTMLCollection rows;
  HTMLElement insertRow(in optional long index);
  void deleteRow(in long index);
           attribute DOMString summary;
};

The table element represents data with more than one dimension, in the form of a table.

The table element takes part in the table model.

Tables must not be used as layout aids. Historically, some Web authors have misused tables in HTML as a way to control their page layout. This usage is non-conforming, because tools attempting to extract tabular data from such documents would obtain very confusing results. In particular, users of accessibility tools like screen readers are likely to find it very difficult to navigate pages with tables used for layout.

There are a variety of alternatives to using HTML tables for layout, primarily using CSS positioning and the CSS table model.

User agents that do table analysis on arbitrary content are encouraged to find heuristics to determine which tables actually contain data and which are merely being used for layout. This specification does not define a precise heuristic.

Tables have rows and columns given by their descendants. A table must not have an empty row or column, as described in the description of the table model.

For tables that consist of more than just a grid of cells with headers in the first row and headers in the first column, and for any table in general where the reader might have difficulty understanding the content, authors should include explanatory information introducing the table. This information is useful for all users, but is especially useful for users who cannot see the table, e.g. users of screen readers.

Such explanatory information should introduce the purpose of the table, outline its basic cell structure, highlight any trends or patterns, and generally teach the user how to use the table.

For instance, the following table:

Characteristics with positive and negative sides
Negative	Characteristic	Positive
Sad	Mood	Happy
Failing	Grade	Passing

...might benefit from a description explaining the way the table is laid out, something like "Characteristics are given in the second column, with the negative side in the left column and the positive side in the right column".

There are a variety of ways to include this information, such as:

In prose, surrounding the table

<p>In the following table, characteristics are given in the second
column, with the negative side in the left column and the positive
side in the right column.</p>
<table>
 <caption>Characteristics with positive and negative sides</caption>
 <thead>
  <tr>
   <th id="n"> Negative
   <th> Characteristic
   <th> Positive
 <tbody>
  <tr>
   <td headers="n r1"> Sad
   <th id="r1"> Mood
   <td> Happy
  <tr>
   <td headers="n r2"> Failing
   <th id="r2"> Grade
   <td> Passing
</table>

In the table's caption

<table>
 <caption>
  <strong>Characteristics with positive and negative sides.</strong>
  <p>Characteristics are given in the second column, with the
  negative side in the left column and the positive side in the right
  column.</p>
 </caption>
 <thead>
  <tr>
   <th id="n"> Negative
   <th> Characteristic
   <th> Positive
 <tbody>
  <tr>
   <td headers="n r1"> Sad
   <th id="r1"> Mood
   <td> Happy
  <tr>
   <td headers="n r2"> Failing
   <th id="r2"> Grade
   <td> Passing
</table>

In the table's caption, in a details element

<table>
 <caption>
  <strong>Characteristics with positive and negative sides.</strong>
  <details>
   <summary>Help</summary>
   <p>Characteristics are given in the second column, with the
   negative side in the left column and the positive side in the right
   column.</p>
  </details>
 </caption>
 <thead>
  <tr>
   <th id="n"> Negative
   <th> Characteristic
   <th> Positive
 <tbody>
  <tr>
   <td headers="n r1"> Sad
   <th id="r1"> Mood
   <td> Happy
  <tr>
   <td headers="n r2"> Failing
   <th id="r2"> Grade
   <td> Passing
</table>

Next to the table, in the same figure

<figure>
 <figcaption>Characteristics with positive and negative sides</figcaption>
 <p>Characteristics are given in the second column, with the
 negative side in the left column and the positive side in the right
 column.</p>
 <table>
  <thead>
   <tr>
    <th id="n"> Negative
    <th> Characteristic
    <th> Positive
  <tbody>
   <tr>
    <td headers="n r1"> Sad
    <th id="r1"> Mood
    <td> Happy
   <tr>
    <td headers="n r2"> Failing
    <th id="r2"> Grade
    <td> Passing
 </table>
</figure>

Next to the table, in a figure's figcaption

<figure>
 <figcaption>
  <strong>Characteristics with positive and negative sides</strong>
  <p>Characteristics are given in the second column, with the
  negative side in the left column and the positive side in the right
  column.</p>
 </figcaption>
 <table>
  <thead>
   <tr>
    <th id="n"> Negative
    <th> Characteristic
    <th> Positive
  <tbody>
   <tr>
    <td headers="n r1"> Sad
    <th id="r1"> Mood
    <td> Happy
   <tr>
    <td headers="n r2"> Failing
    <th id="r2"> Grade
    <td> Passing
 </table>
</figure>

Authors may also use other techniques, or combinations of the above techniques, as appropriate.

The best option, of course, rather than writing a description explaining the way the table is laid out, is to adjust the table such that no explanation is needed.

In the case of the table used in the examples above, a simple rearrangement of the table so that the headers are on the top and left sides removes the need for an explanation as well as removing the need for the use of headers attributes:

<table>
 <caption>Characteristics with positive and negative sides</caption>
 <thead>
  <tr>
   <th> Characteristic
   <th> Negative
   <th> Positive
 <tbody>
  <tr>
   <th> Mood
   <td> Sad
   <td> Happy
  <tr>
   <th> Grade
   <td> Failing
   <td> Passing
</table>

The summary attribute on table elements was suggested in earlier versions of the language as a technique for providing explanatory text for complex tables for users of screen readers. One of the techniques described above should be used instead.

In particular, authors are encouraged to consider whether their explanatory text for tables is likely to be useful to the visually impaired: if their text would not be useful, then it is best to not include a summary attribute. Similarly, if their explanatory text could help someone who is not visually impaired, e.g. someone who is seeing the table for the first time, then the text would be more useful before the table or in the caption. For example, describing the conclusions of the data in a table is useful to everyone; explaining how to read the table, if not obvious from the headers alone, is useful to everyone; describing the structure of the table, if it is easy to grasp visually, may not be useful to everyone, but it might also not be useful to users who can quickly navigate the table with an accessibility tool.

If a table element has a summary attribute, the user agent may report the contents of that attribute to the user.

table . caption [ = value ]

Returns the table's caption element.

Can be set, to replace the caption element. If the new value is not a caption element, throws a HIERARCHY_REQUEST_ERR exception.

caption = table . createCaption()

Ensures the table has a caption element, and returns it.

table . deleteCaption()

Ensures the table does not have a caption element.

table . tHead [ = value ]

Returns the table's thead element.

Can be set, to replace the thead element. If the new value is not a thead element, throws a HIERARCHY_REQUEST_ERR exception.

thead = table . createTHead()

Ensures the table has a thead element, and returns it.

table . deleteTHead()

Ensures the table does not have a thead element.

table . tFoot [ = value ]

Returns the table's tfoot element.

Can be set, to replace the tfoot element. If the new value is not a tfoot element, throws a HIERARCHY_REQUEST_ERR exception.

tfoot = table . createTFoot()

Ensures the table has a tfoot element, and returns it.

table . deleteTFoot()

Ensures the table does not have a tfoot element.

table . tBodies

Returns an HTMLCollection of the tbody elements of the table.

tbody = table . createTBody()

Creates a tbody element, inserts it into the table, and returns it.

table . rows

Returns an HTMLCollection of the tr elements of the table.

tr = table . insertRow(index)

Creates a tr element, along with a tbody if required, inserts them into the table at the position given by the argument, and returns the tr.

The position is relative to the rows in the table. The index −1 is equivalent to inserting at the end of the table.

If the given position is less than −1 or greater than the number of rows, throws an INDEX_SIZE_ERR exception.

table . deleteRow(index)

Removes the tr element with the given position in the table.

The position is relative to the rows in the table. The index −1 is equivalent to deleting the last row of the table.

If the given position is less than −1 or greater than the index of the last row, or if there are no rows, throws an INDEX_SIZE_ERR exception.

The caption IDL attribute must return, on getting, the first caption element child of the table element, if any, or null otherwise. On setting, if the new value is a caption element, the first caption element child of the table element, if any, must be removed, and the new value must be inserted as the first node of the table element. If the new value is not a caption element, then a HIERARCHY_REQUEST_ERR DOM exception must be raised instead.

The createCaption() method must return the first caption element child of the table element, if any; otherwise a new caption element must be created, inserted as the first node of the table element, and then returned.

The deleteCaption() method must remove the first caption element child of the table element, if any.

The tHead IDL attribute must return, on getting, the first thead element child of the table element, if any, or null otherwise. On setting, if the new value is a thead element, the first thead element child of the table element, if any, must be removed, and the new value must be inserted immediately before the first element in the table element that is neither a caption element nor a colgroup element, if any, or at the end of the table if there are no such elements. If the new value is not a thead element, then a HIERARCHY_REQUEST_ERR DOM exception must be raised instead.

The createTHead() method must return the first thead element child of the table element, if any; otherwise a new thead element must be created and inserted immediately before the first element in the table element that is neither a caption element nor a colgroup element, if any, or at the end of the table if there are no such elements, and then that new element must be returned.

The deleteTHead() method must remove the first thead element child of the table element, if any.

The tFoot IDL attribute must return, on getting, the first tfoot element child of the table element, if any, or null otherwise. On setting, if the new value is a tfoot element, the first tfoot element child of the table element, if any, must be removed, and the new value must be inserted immediately before the first element in the table element that is neither a caption element, a colgroup element, nor a thead element, if any, or at the end of the table if there are no such elements. If the new value is not a tfoot element, then a HIERARCHY_REQUEST_ERR DOM exception must be raised instead.

The createTFoot() method must return the first tfoot element child of the table element, if any; otherwise a new tfoot element must be created and inserted immediately before the first element in the table element that is neither a caption element, a colgroup element, nor a thead element, if any, or at the end of the table if there are no such elements, and then that new element must be returned.

The deleteTFoot() method must remove the first tfoot element child of the table element, if any.

The tBodies attribute must return an HTMLCollection rooted at the table node, whose filter matches only tbody elements that are children of the table element.

The createTBody() method must create a new tbody element, insert it immediately after the last tbody element in the table element, if any, or at the end of the table element if the table element has no tbody element children, and then must return the new tbody element.

The rows attribute must return an HTMLCollection rooted at the table node, whose filter matches only tr elements that are either children of the table element, or children of thead, tbody, or tfoot elements that are themselves children of the table element. The elements in the collection must be ordered such that those elements whose parent is a thead are included first, in tree order, followed by those elements whose parent is either a table or tbody element, again in tree order, followed finally by those elements whose parent is a tfoot element, still in tree order.

The behavior of the insertRow(index) method depends on the state of the table. When it is called, the method must act as required by the first item in the following list of conditions that describes the state of the table and the index argument:

If index is less than −1 or greater than the number of elements in rows collection:: The method must raise an INDEX_SIZE_ERR exception.
If the rows collection has zero elements in it, and the table has no tbody elements in it:: The method must create a tbody element, then create a tr element, then append the tr element to the tbody element, then append the tbody element to the table element, and finally return the tr element.
If the rows collection has zero elements in it:: The method must create a tr element, append it to the last tbody element in the table, and return the tr element.
If index is missing, equal to −1, or equal to the number of items in rows collection:: The method must create a tr element, and append it to the parent of the last tr element in the rows collection. Then, the newly created tr element must be returned.
Otherwise:: The method must create a tr element, insert it immediately before the indexth tr element in the rows collection, in the same parent, and finally must return the newly created tr element.

When the deleteRow(index) method is called, the user agent must run the following steps:

If index is equal to −1, then index must be set to the number if items in the rows collection, minus one.
Now, if index is less than zero, or greater than or equal to the number of elements in the rows collection, the method must instead raise an INDEX_SIZE_ERR exception, and these steps must be aborted.
Otherwise, the method must remove the indexth element in the rows collection from its parent.

The summary IDL attribute must reflect the content attribute of the same name.

4.9.2 The `caption` element

Status: Last call for comments

Categories

None.

Contexts in which this element may be used:

As the first element child of a table element.

Content model:

Flow content, but with no descendant table elements.

Content attributes:

DOM interface:

interface HTMLTableCaptionElement : HTMLElement {};

The caption element represents the title of the table that is its parent, if it has a parent and that is a table element.

The caption element takes part in the table model.

When a table element is the only content in a figure element other than the figcaption, the caption element should be omitted in favor of the figcaption.

A caption can introduce context for a table, making it significantly easier to understand.

Consider, for instance, the following table:

	1	2	3	4	5	6
1	2	3	4	5	6	7
2	3	4	5	6	7	8
3	4	5	6	7	8	9
4	5	6	7	8	9	10
5	6	7	8	9	10	11
6	7	8	9	10	11	12

In the abstract, this table is not clear. However, with a caption giving the table's number (for reference in the main prose) and explaining its use, it makes more sense:

<caption>
<p>Table 1.
<p>This table shows the total score obtained from rolling two
six-sided dice. The first row represents the value of the first die,
the first column the value of the second die. The total is given in
the cell that corresponds to the values of the two dice.
</caption>

4.9.3 The `colgroup` element

Status: Last call for comments

Categories

None.

Contexts in which this element may be used:

As a child of a table element, after any caption elements and before any thead, tbody, tfoot, and tr elements.

Content model:

If the span attribute is present: Empty.

If the span attribute is absent: Zero or more col elements.

Content attributes:

span

DOM interface:

interface HTMLTableColElement : HTMLElement {
           attribute unsigned long span;
};

The colgroup element represents a group of one or more columns in the table that is its parent, if it has a parent and that is a table element.

If the colgroup element contains no col elements, then the element may have a span content attribute specified, whose value must be a valid non-negative integer greater than zero.

The colgroup element and its span attribute take part in the table model.

The span IDL attribute must reflect the content attribute of the same name. The value must be limited to only non-negative numbers greater than zero.

4.9.4 The `col` element

Status: Last call for comments

Categories: None.
Contexts in which this element may be used:: As a child of a colgroup element that doesn't have a span attribute.
Content model:: Empty.
Content attributes:: Global attributes; span
DOM interface:: HTMLTableColElement, same as for colgroup elements. This interface defines one member, span.

If a col element has a parent and that is a colgroup element that itself has a parent that is a table element, then the col element represents one or more columns in the column group represented by that colgroup.

The element may have a span content attribute specified, whose value must be a valid non-negative integer greater than zero.

The col element and its span attribute take part in the table model.

The span IDL attribute must reflect the content attribute of the same name. The value must be limited to only non-negative numbers greater than zero.

4.9.5 The `tbody` element

Status: Last call for comments

Categories

None.

Contexts in which this element may be used:

As a child of a table element, after any caption, colgroup, and thead elements, but only if there are no tr elements that are children of the table element.

Content model:

Zero or more tr elements

Content attributes:

DOM interface:

interface HTMLTableSectionElement : HTMLElement {
  readonly attribute HTMLCollection rows;
  HTMLElement insertRow(in optional long index);
  void deleteRow(in long index);
};

The HTMLTableSectionElement interface is also used for thead and tfoot elements.

The tbody element represents a block of rows that consist of a body of data for the parent table element, if the tbody element has a parent and it is a table.

The tbody element takes part in the table model.

tbody . rows

Returns an HTMLCollection of the tr elements of the table section.

tr = tbody . insertRow( [ index ] )

Creates a tr element, inserts it into the table section at the position given by the argument, and returns the tr.

The position is relative to the rows in the table section. The index −1, which is the default if the argument is omitted, is equivalent to inserting at the end of the table section.

If the given position is less than −1 or greater than the number of rows, throws an INDEX_SIZE_ERR exception.

tbody . deleteRow(index)

Removes the tr element with the given position in the table section.

The position is relative to the rows in the table section. The index −1 is equivalent to deleting the last row of the table section.

If the given position is less than −1 or greater than the index of the last row, or if there are no rows, throws an INDEX_SIZE_ERR exception.

The rows attribute must return an HTMLCollection rooted at the element, whose filter matches only tr elements that are children of the element.

The insertRow(index) method must, when invoked on an element table section, act as follows:

If index is less than −1 or greater than the number of elements in the rows collection, the method must raise an INDEX_SIZE_ERR exception.

If index is missing, equal to −1, or equal to the number of items in the rows collection, the method must create a tr element, append it to the element table section, and return the newly created tr element.

Otherwise, the method must create a tr element, insert it as a child of the table section element, immediately before the indexth tr element in the rows collection, and finally must return the newly created tr element.

The deleteRow(index) method must remove the indexth element in the rows collection from its parent. If index is less than zero or greater than or equal to the number of elements in the rows collection, the method must instead raise an INDEX_SIZE_ERR exception.

4.9.6 The `thead` element

Status: Last call for comments

Categories: None.
Contexts in which this element may be used:: As a child of a table element, after any caption, and colgroup elements and before any tbody, tfoot, and tr elements, but only if there are no other thead elements that are children of the table element.
Content model:: Zero or more tr elements
Content attributes:: Global attributes
DOM interface:: HTMLTableSectionElement, as defined for tbody elements.

The thead element represents the block of rows that consist of the column labels (headers) for the parent table element, if the thead element has a parent and it is a table.

The thead element takes part in the table model.

4.9.7 The `tfoot` element

Status: Last call for comments

Categories: None.
Contexts in which this element may be used:: As a child of a table element, after any caption, colgroup, and thead elements and before any tbody and tr elements, but only if there are no other tfoot elements that are children of the table element.; As a child of a table element, after any caption, colgroup, thead, tbody, and tr elements, but only if there are no other tfoot elements that are children of the table element.
Content model:: Zero or more tr elements
Content attributes:: Global attributes
DOM interface:: HTMLTableSectionElement, as defined for tbody elements.

The tfoot element represents the block of rows that consist of the column summaries (footers) for the parent table element, if the tfoot element has a parent and it is a table.

The tfoot element takes part in the table model.

4.9.8 The `tr` element

Status: Last call for comments

Categories

None.

Contexts in which this element may be used:

As a child of a thead element.

As a child of a tbody element.

As a child of a tfoot element.

As a child of a table element, after any caption, colgroup, and thead elements, but only if there are no tbody elements that are children of the table element.

Content model:

When the parent node is a thead element: Zero or more th elements

Otherwise: Zero or more td or th elements

Content attributes:

DOM interface:

interface HTMLTableRowElement : HTMLElement {
  readonly attribute long rowIndex;
  readonly attribute long sectionRowIndex;
  readonly attribute HTMLCollection cells;
  HTMLElement insertCell(in optional long index);
  void deleteCell(in long index);
};

The tr element represents a row of cells in a table.

The tr element takes part in the table model.

tr . rowIndex

Returns the position of the row in the table's rows list.

Returns −1 if the element isn't in a table.

tr . sectionRowIndex

Returns the position of the row in the table section's rows list.

Returns −1 if the element isn't in a table section.

tr . cells

Returns an HTMLCollection of the td and th elements of the row.

cell = tr . insertCell( [ index ] )

Creates a td element, inserts it into the table row at the position given by the argument, and returns the td.

The position is relative to the cells in the row. The index −1, which is the default if the argument is omitted, is equivalent to inserting at the end of the row.

If the given position is less than −1 or greater than the number of cells, throws an INDEX_SIZE_ERR exception.

tr . deleteCell(index)

Removes the td or th element with the given position in the row.

The position is relative to the cells in the row. The index −1 is equivalent to deleting the last cell of the row.

If the given position is less than −1 or greater than the index of the last cell, or if there are no cells, throws an INDEX_SIZE_ERR exception.

The rowIndex attribute must, if the element has a parent table element, or a parent tbody, thead, or tfoot element and a grandparent table element, return the index of the tr element in that table element's rows collection. If there is no such table element, then the attribute must return −1.

The sectionRowIndex attribute must, if the element has a parent table, tbody, thead, or tfoot element, return the index of the tr element in the parent element's rows collection (for tables, that's the rows collection; for table sections, that's the rows collection). If there is no such parent element, then the attribute must return −1.

The cells attribute must return an HTMLCollection rooted at the tr element, whose filter matches only td and th elements that are children of the tr element.

The insertCell(index) method must act as follows:

If index is less than −1 or greater than the number of elements in the cells collection, the method must raise an INDEX_SIZE_ERR exception.

If index is missing, equal to −1, or equal to the number of items in cells collection, the method must create a td element, append it to the tr element, and return the newly created td element.

Otherwise, the method must create a td element, insert it as a child of the tr element, immediately before the indexth td or th element in the cells collection, and finally must return the newly created td element.

The deleteCell(index) method must remove the indexth element in the cells collection from its parent. If index is less than zero or greater than or equal to the number of elements in the cells collection, the method must instead raise an INDEX_SIZE_ERR exception.

4.9.9 The `td` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

As a child of a tr element.

Content model:

Content attributes:

colspan

rowspan

headers

DOM interface:

interface HTMLTableDataCellElement : HTMLTableCellElement {};

The td element represents a data cell in a table.

The td element and its colspan, rowspan, and headers attributes take part in the table model.

4.9.10 The `th` element

Status: Last call for comments

Categories

None.

Contexts in which this element may be used:

As a child of a tr element.

Content model:

Content attributes:

colspan

rowspan

headers

scope

DOM interface:

interface HTMLTableHeaderCellElement : HTMLTableCellElement {
           attribute DOMString scope;
};

The th element represents a header cell in a table.

The th element may have a scope content attribute specified. The scope attribute is an enumerated attribute with five states, four of which have explicit keywords:

The row keyword, which maps to the row state: The row state means the header cell applies to some of the subsequent cells in the same row(s).
The col keyword, which maps to the column state: The column state means the header cell applies to some of the subsequent cells in the same column(s).
The rowgroup keyword, which maps to the row group state: The row group state means the header cell applies to all the remaining cells in the row group. A th element's scope attribute must not be in the row group state if the element is not anchored in a row group.
The colgroup keyword, which maps to the column group state: The column group state means the header cell applies to all the remaining cells in the column group. A th element's scope attribute must not be in the column group state if the element is not anchored in a column group.
The auto state: The auto state makes the header cell apply to a set of cells selected based on context.

The scope attribute's missing value default is the auto state.

The th element and its colspan, rowspan, headers, and scope attributes take part in the table model.

The scope IDL attribute must reflect the content attribute of the same name.

The following example shows how the scope attribute's rowgroup value affects which data cells a header cell applies to.

Here is a markup fragment showing a table:

<table>
 <thead>
  <tr> <th> ID <th> Measurement <th> Average <th> Maximum
 <tbody>
  <tr> <td> <th scope=rowgroup> Cats <td> <td>
  <tr> <td> 93 <th> Legs <td> 3.5 <td> 4
  <tr> <td> 10 <th> Tails <td> 1 <td> 1
 <tbody>
  <tr> <td> <th scope=rowgroup> English speakers <td> <td>
  <tr> <td> 32 <th> Legs <td> 2.67 <td> 4
  <tr> <td> 35 <th> Tails <td> 0.33 <td> 1
</table>

This would result in the following table:

ID	Measurement	Average	Maximum
	Cats
93	Legs	3.5	4
10	Tails	1	1
	English speakers
32	Legs	2.67	4
35	Tails	0.33	1

The headers in the first row all apply directly down to the rows in their column.

The headers with the explicit scope attributes apply to all the cells in their row group other than the cells in the first column.

The remaining headers apply just to the cells to the right of them.

4.9.11 Attributes common to `td` and `th` elements

Status: Last call for comments

The td and th elements may have a colspan content attribute specified, whose value must be a valid non-negative integer greater than zero.

The td and th elements may also have a rowspan content attribute specified, whose value must be a valid non-negative integer.

These attributes give the number of columns and rows respectively that the cell is to span. These attributes must not be used to overlap cells, as described in the description of the table model.

The td and th element may have a headers content attribute specified. The headers attribute, if specified, must contain a string consisting of an unordered set of unique space-separated tokens, each of which must have the value of an ID of a th element taking part in the same table as the td or th element (as defined by the table model).

A th element with ID id is said to be directly targeted by all td and th elements in the same table that have headers attributes whose values include as one of their tokens the ID id. A th element A is said to be targeted by a th or td element B if either A is directly targeted by B or if there exists an element C that is itself targeted by the element B and A is directly targeted by C.

A th element must not be targeted by itself.

The colspan, rowspan, and headers attributes take part in the table model.

The td and th elements implement interfaces that inherit from the HTMLTableCellElement interface:

interface HTMLTableCellElement : HTMLElement {
           attribute unsigned long colSpan;
           attribute unsigned long rowSpan;
  [PutForwards=value] readonly attribute DOMSettableTokenList headers;
  readonly attribute long cellIndex;
};

cell . cellIndex

Returns the position of the cell in the row's cells list.

Returns 0 if the element isn't in a row.

The colSpan IDL attribute must reflect the content attribute of the same name. The value must be limited to only non-negative numbers greater than zero.

The rowSpan IDL attribute must reflect the content attribute of the same name. Its default value, which must be used if parsing the attribute as a non-negative integer returns an error, is 1.

The headers IDL attribute must reflect the content attribute of the same name.

The cellIndex IDL attribute must, if the element has a parent tr element, return the index of the cell's element in the parent element's cells collection. If there is no such parent element, then the attribute must return 0.

4.9.12 Processing model

Status: Last call for comments

The various table elements and their content attributes together define the table model.

A table consists of cells aligned on a two-dimensional grid of slots with coordinates (x, y). The grid is finite, and is either empty or has one or more slots. If the grid has one or more slots, then the x coordinates are always in the range 0 ≤ x < x_width, and the y coordinates are always in the range 0 ≤ y < y_height. If one or both of x_width and y_height are zero, then the table is empty (has no slots). Tables correspond to table elements.

A cell is a set of slots anchored at a slot (cell_x, cell_y), and with a particular width and height such that the cell covers all the slots with coordinates (x, y) where cell_x ≤ x < cell_x+width and cell_y ≤ y < cell_y+height. Cells can either be data cells or header cells. Data cells correspond to td elements, and header cells correspond to th elements. Cells of both types can have zero or more associated header cells.

It is possible, in certain error cases, for two cells to occupy the same slot.

A row is a complete set of slots from x=0 to x=x_width-1, for a particular value of y. Rows correspond to tr elements.

A column is a complete set of slots from y=0 to y=y_height-1, for a particular value of x. Columns can correspond to col elements, but in the absence of col elements are implied.

A row group is a set of rows anchored at a slot (0, group_y) with a particular height such that the row group covers all the slots with coordinates (x, y) where 0 ≤ x < x_width and group_y ≤ y < group_y+height. Row groups correspond to tbody, thead, and tfoot elements. Not every row is necessarily in a row group.

A column group is a set of columns anchored at a slot (group_x, 0) with a particular width such that the column group covers all the slots with coordinates (x, y) where group_x ≤ x < group_x+width and 0 ≤ y < y_height. Column groups correspond to colgroup elements. Not every column is necessarily in a column group.

Row groups cannot overlap each other. Similarly, column groups cannot overlap each other.

A cell cannot cover slots that are from two or more row groups. It is, however, possible for a cell to be in multiple column groups. All the slots that form part of one cell are part of zero or one row groups and zero or more column groups.

In addition to cells, columns, rows, row groups, and column groups, tables can have a caption element associated with them. This gives the table a heading, or legend.

A table model error is an error with the data represented by table elements and their descendants. Documents must not have table model errors.

4.9.12.1 Forming a table

Status: Last call for comments

To determine which elements correspond to which slots in a table associated with a table element, to determine the dimensions of the table (x_width and y_height), and to determine if there are any table model errors, user agents must use the following algorithm:

Let x_width be zero.
Let y_height be zero.
Let pending tfoot elements be a list of tfoot elements, initially empty.
Let the table be the table represented by the table element. The x_width and y_height variables give the table's dimensions. The table is initially empty.
If the table element has no children elements, then return the table (which will be empty), and abort these steps.
Associate the first caption element child of the table element with the table. If there are no such children, then it has no associated caption element.
Let the current element be the first element child of the table element.

If a step in this algorithm ever requires the current element to be advanced to the next child of the table when there is no such next child, then the user agent must jump to the step labeled end, near the end of this algorithm.
While the current element is not one of the following elements, advance the current element to the next child of the table:
- colgroup
- thead
- tbody
- tfoot
- tr
If the current element is a colgroup, follow these substeps:
1. Column groups: Process the current element according to the appropriate case below:
  If the current element has any col element children
  Follow these steps:
  1. Let x_start have the value of x_width.
  2. Let the current column be the first col element child of the colgroup element.
  3. Columns: If the current column col element has a span attribute, then parse its value using the rules for parsing non-negative integers.
    
    If the result of parsing the value is not an error or zero, then let span be that value.
    
    Otherwise, if the col element has no span attribute, or if trying to parse the attribute's value resulted in an error or zero, then let span be 1.
  4. Increase x_width by span.
  5. Let the last span columns in the table correspond to the current column col element.
  6. If current column is not the last col element child of the colgroup element, then let the current column be the next col element child of the colgroup element, and return to the step labeled columns.
  7. Let all the last columns in the table from x=x_start to x=x_width-1 form a new column group, anchored at the slot (x_start, 0), with width x_width-x_start, corresponding to the colgroup element.
  If the current element has no col element children
  1. If the colgroup element has a span attribute, then parse its value using the rules for parsing non-negative integers.
    
    If the result of parsing the value is not an error or zero, then let span be that value.
    
    Otherwise, if the colgroup element has no span attribute, or if trying to parse the attribute's value resulted in an error or zero, then let span be 1.
  2. Increase x_width by span.
  3. Let the last span columns in the table form a new column group, anchored at the slot (x_width-span, 0), with width span, corresponding to the colgroup element.
2. Advance the current element to the next child of the table.
3. While the current element is not one of the following elements, advance the current element to the next child of the table:
  - colgroup
  - thead
  - tbody
  - tfoot
  - tr
4. If the current element is a colgroup element, jump to the step labeled column groups above.
Let y_current be zero.
Let the list of downward-growing cells be an empty list.
Rows: While the current element is not one of the following elements, advance the current element to the next child of the table:
- thead
- tbody
- tfoot
- tr
If the current element is a tr, then run the algorithm for processing rows, advance the current element to the next child of the table, and return to the step labeled rows.
Run the algorithm for ending a row group.
If the current element is a tfoot, then add that element to the list of pending tfoot elements, advance the current element to the next child of the table, and return to the step labeled rows.
The current element is either a thead or a tbody.

Run the algorithm for processing row groups.
Advance the current element to the next child of the table.
Return to the step labeled rows.
End: For each tfoot element in the list of pending tfoot elements, in tree order, run the algorithm for processing row groups.
If there exists a row or column in the table containing only slots that do not have a cell anchored to them, then this is a table model error.
Return the table.

The algorithm for processing row groups, which is invoked by the set of steps above for processing thead, tbody, and tfoot elements, is:

Let y_start have the value of y_height.
For each tr element that is a child of the element being processed, in tree order, run the algorithm for processing rows.
If y_height > y_start, then let all the last rows in the table from y=y_start to y=y_height-1 form a new row group, anchored at the slot with coordinate (0, y_start), with height y_height-y_start, corresponding to the element being processed.
Run the algorithm for ending a row group.

The algorithm for ending a row group, which is invoked by the set of steps above when starting and ending a block of rows, is:

While y_current is less than y_height, follow these steps:
1. Run the algorithm for growing downward-growing cells.
2. Increase y_current by 1.
Empty the list of downward-growing cells.

The algorithm for processing rows, which is invoked by the set of steps above for processing tr elements, is:

If y_height is equal to y_current, then increase y_height by 1. (y_current is never greater than y_height.)
Let x_current be 0.
Run the algorithm for growing downward-growing cells.
If the tr element being processed has no td or th element children, then increase y_current by 1, abort this set of steps, and return to the algorithm above.
Let current cell be the first td or th element in the tr element being processed.
Cells: While x_current is less than x_width and the slot with coordinate (x_current, y_current) already has a cell assigned to it, increase x_current by 1.
If x_current is equal to x_width, increase x_width by 1. (x_current is never greater than x_width.)
If the current cell has a colspan attribute, then parse that attribute's value, and let colspan be the result.

If parsing that value failed, or returned zero, or if the attribute is absent, then let colspan be 1, instead.
If the current cell has a rowspan attribute, then parse that attribute's value, and let rowspan be the result.

If parsing that value failed or if the attribute is absent, then let rowspan be 1, instead.
If rowspan is zero, then let cell grows downward be true, and set rowspan to 1. Otherwise, let cell grows downward be false.
If x_width < x_current+colspan, then let x_width be x_current+colspan.
If y_height < y_current+rowspan, then let y_height be y_current+rowspan.
Let the slots with coordinates (x, y) such that x_current ≤ x < x_current+colspan and y_current ≤ y < y_current+rowspan be covered by a new cell c, anchored at (x_current, y_current), which has width colspan and height rowspan, corresponding to the current cell element.

If the current cell element is a th element, let this new cell c be a header cell; otherwise, let it be a data cell.

To establish which header cells apply to the current cell element, use the algorithm for assigning header cells described in the next section.

If any of the slots involved already had a cell covering them, then this is a table model error. Those slots now have two cells overlapping.
If cell grows downward is true, then add the tuple {c, x_current, colspan} to the list of downward-growing cells.
Increase x_current by colspan.
If current cell is the last td or th element in the tr element being processed, then increase y_current by 1, abort this set of steps, and return to the algorithm above.
Let current cell be the next td or th element in the tr element being processed.
Return to the step labelled cells.

When the algorithms above require the user agent to run the algorithm for growing downward-growing cells, the user agent must, for each {cell, cell_x, width} tuple in the list of downward-growing cells, if any, extend the cell cell so that it also covers the slots with coordinates (x, y_current), where cell_x ≤ x < cell_x+width.

4.9.12.2 Forming relationships between data cells and header cells

Status: Last call for comments

Each cell can be assigned zero or more header cells. The algorithm for assigning header cells to a cell principal cell is as follows.

Let header list be an empty list of cells.
Let (principal_x, principal_y) be the coordinate of the slot to which the principal cell is anchored.
If the principal cell has a headers attribute specified
1. Take the value of the principal cell's headers attribute and split it on spaces, letting id list be the list of tokens obtained.
2. For each token in the id list, if the first element in the Document with an ID equal to the token is a cell in the same table, and that cell is not the principal cell, then add that cell to header list.
If principal cell does not have a headers attribute specified
1. Let principal_width be the width of the principal cell.
2. Let principal_height be the height of the principal cell.
3. For each value of y from principal_y to principal_y+principal_height-1, run the internal algorithm for scanning and assigning header cells, with the principal cell, the header list, the initial coordinate (principal_x,y), and the increments Δx=−1 and Δy=0.
4. For each value of x from principal_x to principal_x+principal_width-1, run the internal algorithm for scanning and assigning header cells, with the principal cell, the header list, the initial coordinate (x,principal_y), and the increments Δx=0 and Δy=−1.
5. If the principal cell is anchored in a row group, then add all header cells that are row group headers and are anchored in the same row group with an x-coordinate less than or equal to principal_x+principal_width-1 and a y-coordinate less than or equal to principal_y+principal_height-1 to header list.
6. If the principal cell is anchored in a column group, then add all header cells that are column group headers and are anchored in the same column group with an x-coordinate less than or equal to principal_x+principal_width-1 and a y-coordinate less than or equal to principal_y+principal_height-1 to header list.
Remove all the empty cells from the header list.
Remove any duplicates from the header list.
Remove principal cell from the header list if it is there.
Assign the headers in the header list to the principal cell.

The internal algorithm for scanning and assigning header cells, given a principal cell, a header list, an initial coordinate (initial_x, initial_y), and Δx and Δy increments, is as follows:

Let x equal initial_x.
Let y equal initial_y.
Let opaque headers be an empty list of cells.
If principal cell is a header cell

Let in header block be true, and let headers from current header block be a list of cells containing just the principal cell.

Otherwise

Let in header block be false and let headers from current header block be an empty list of cells.
Loop: Increment x by Δx; increment y by Δy.

For each invocation of this algorithm, one of Δx and Δy will be −1, and the other will be 0.
If either x or y is less than 0, then abort this internal algorithm.
If there is no cell covering slot (x, y), or if there is more than one cell covering slot (x, y), return to the substep labeled loop.
Let current cell be the cell covering slot (x, y).
If current cell is a header cell
1. Set in header block to true.
2. Add current cell to headers from current header block.
3. Let blocked be false.
4. If Δx is 0
  
  If there are any cells in the opaque headers list anchored with the same x-coordinate as the current cell, and with the same width as current cell, then let blocked be true.
  
  If the current cell is not a column header, then let blocked be true.
  
  If Δy is 0
  
  If there is are any cells in the opaque headers list anchored with the same y-coordinate as the current cell, and with the same height as current cell, then let blocked be true.
  
  If the current cell is not a row header, then let blocked be true.
5. If blocked is false, then add the current cell to the headers list.
If current cell is a data cell and in header block is true

Set in header block to false. Add all the cells in headers from current header block to the opaque headers list, and empty the headers from current header block list.
Return to the step labeled loop.

A header cell anchored at the slot with coordinate (x, y) with width width and height height is said to be a column header if any of the following conditions are true:

The cell's scope attribute is in the column state, or
The cell's scope attribute is in the auto state, and there are no data cells in any of the cells covering slots with y-coordinates y .. y+height-1.

A header cell anchored at the slot with coordinate (x, y) with width width and height height is said to be a row header if any of the following conditions are true:

The cell's scope attribute is in the row state, or
The cell's scope attribute is in the auto state, the cell is not a column header, and there are no data cells in any of the cells covering slots with x-coordinates x .. x+width-1.

A header cell is said to be a column group header if its scope attribute is in the column group state.

A header cell is said to be a row group header if its scope attribute is in the row group state.

A cell is said to be an empty cell if it contains no elements and its text content, if any, consists only of White_Space characters.

4.9.13 Examples

Status: Last call for comments

This section is non-normative.

The following shows how might one mark up the bottom part of table 45 of the Smithsonian physical tables, Volume 71:

<table>
 <caption>Specification values: <b>Steel</b>, <b>Castings</b>,
 Ann. A.S.T.M. A27-16, Class B;* P max. 0.06; S max. 0.05.</caption>
 <thead>
  <tr>
   <th rowspan=2>Grade.</th>
   <th rowspan=2>Yield Point.</th>
   <th colspan=2>Ultimate tensile strength</th>
   <th rowspan=2>Per sent elong. 50.8mm or 2 in.</th>
   <th rowspan=2>Per cent reduct. area.</th>
  </tr>
  <tr>
   <th>kg/mm<sup>2</sup></th>
   <th>lb/in<sup>2</sup></th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td>Hard</td>
   <td>0.45 ultimate</td>
   <td>56.2</td>
   <td>80,000</td>
   <td>15</td>
   <td>20</td>
  </tr>
  <tr>
   <td>Medium</td>
   <td>0.45 ultimate</td>
   <td>49.2</td>
   <td>70,000</td>
   <td>18</td>
   <td>25</td>
  </tr>
  <tr>
   <td>Soft</td>
   <td>0.45 ultimate</td>
   <td>42.2</td>
   <td>60,000</td>
   <td>22</td>
   <td>30</td>
  </tr>
 </tbody>
</table>

This table could look like this:

Specification values: **Steel**, **Castings**, Ann. A.S.T.M. A27-16, Class B;* P max. 0.06; S max. 0.05.
Grade.	Yield Point.	Ultimate tensile strength		Per cent elong. 50.8 mm or 2 in.	Per cent reduct. area.
Grade.	Yield Point.	kg/mm²	lb/in²	Per cent elong. 50.8 mm or 2 in.	Per cent reduct. area.
Hard	0.45 ultimate	56.2	80,000	15	20
Medium	0.45 ultimate	49.2	70,000	18	25
Soft	0.45 ultimate	42.2	60,000	22	30

The following shows how one might mark up the gross margin table on page 46 of Apple, Inc's 10-K filing for fiscal year 2008:

<table>
 <thead>
  <tr>
   <th>
   <th>2008
   <th>2007
   <th>2006
 <tbody>
  <tr>
   <th>Net sales
   <td>$ 32,479
   <td>$ 24,006
   <td>$ 19,315
  <tr>
   <th>Cost of sales
   <td>  21,334
   <td>  15,852
   <td>  13,717
 <tbody>
  <tr>
   <th>Gross margin
   <td>$ 11,145
   <td>$  8,154
   <td>$  5,598
 <tfoot>
  <tr>
   <th>Gross margin percentage
   <td>34.3%
   <td>34.0%
   <td>29.0%
</table>

The following shows how one might mark up the operating expenses table from lower on the same page of that document:

<table>
 <colgroup> <col>
 <colgroup> <col> <col> <col>
 <thead>
  <tr> <th> <th>2008 <th>2007 <th>2006
 <tbody>
  <tr> <th scope=rowgroup> Research and development
       <td> $ 1,109 <td> $ 782 <td> $ 712 
  <tr> <th scope=row> Percentage of net sales
       <td> 3.4% <td> 3.3% <td> 3.7% 
 <tbody>
  <tr> <th scope=rowgroup> Selling, general, and administrative
       <td> $ 3,761 <td> $ 2,963 <td> $ 2,433 
  <tr> <th scope=row> Percentage of net sales
       <td> 11.6% <td> 12.3% <td> 12.6%
</table>

This table could look like this:

	2008	2007	2006
Research and development	$ 1,109	$ 782	$ 712
Percentage of net sales	3.4%	3.3%	3.7%
Selling, general, and administrative	$ 3,761	$ 2,963	$ 2,433
Percentage of net sales	11.6%	12.3%	12.6%

4.10 Forms

Status: Last call for comments

4.10.1 Introduction

Status: Last call for comments

This section is non-normative.

Forms allow unscripted client-server interaction: given a form, a user can provide data, submit it to the server, and have the server act on it accordingly (e.g. returning the results of a search or calculation). The elements used in forms can also be used for user interaction with no associated submission mechanism, in conjunction with scripts.

Writing a form consists of several steps, which can be performed in any order: writing the user interface, implementing the server-side processing, and configuring the user interface to communicate with the server.

4.10.1.1 Writing a form's user interface

This section is non-normative.

For the purposes of this brief introduction, we will create a pizza ordering form.

Any form starts with a form element, inside which are placed the controls. Most controls are represented by the input element, which by default provides a one-line text field. To label a control, the label element is used; the label text and the control itself go inside the label element. Each part of a form is considered a paragraph, and is typically separated from other parts using p elements. Putting this together, here is how one might ask for the customer's name:

<form>
 <p><label>Customer name: <input></label></p>
</form>

To let the user select the size of the pizza, we can use a set of radio buttons. Radio buttons also use the input element, this time with a type attribute with the value radio. To make the radio buttons work as a group, they are given a common name using the name attribute. To group a batch of controls together, such as, in this case, the radio buttons, one can use the fieldset element. The title of such a group of controls is given by the first element in the fieldset, which has to be a legend element.

<form>
 <p><label>Customer name: <input></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
</form>

Changes from the previous step are highlighted.

To pick toppings, we can use checkboxes. These use the input element with a type attribute with the value checkbox:

<form>
 <p><label>Customer name: <input></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox> Bacon </label></p>
  <p><label> <input type=checkbox> Extra Cheese </label></p>
  <p><label> <input type=checkbox> Onion </label></p>
  <p><label> <input type=checkbox> Mushroom </label></p>
 </fieldset>
</form>

The pizzeria for which this form is being written is always making mistakes, so it needs a way to contact the customer. For this purpose, we can use form controls specifically for telephone numbers (input elements with their type attribute set to tel) and e-mail addresses (input elements with their type attribute set to email):

<form>
 <p><label>Customer name: <input></label></p>
 <p><label>Telephone: <input type=tel></label></p>
 <p><label>E-mail address: <input type=email></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox> Bacon </label></p>
  <p><label> <input type=checkbox> Extra Cheese </label></p>
  <p><label> <input type=checkbox> Onion </label></p>
  <p><label> <input type=checkbox> Mushroom </label></p>
 </fieldset>
</form>

We can use an input element with its type attribute set to time to ask for a delivery time. Many of these form controls have attributes to control exactly what values can be specified; in this case, three attributes of particular interest are min, max, and step. These set the minimum time, the maximum time, and the interval between allowed values (in seconds). This pizzeria only delivers between 11am and 9pm, and doesn't promise anything better than 15 minute increments, which we can mark up as follows:

<form>
 <p><label>Customer name: <input></label></p>
 <p><label>Telephone: <input type=tel></label></p>
 <p><label>E-mail address: <input type=email></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox> Bacon </label></p>
  <p><label> <input type=checkbox> Extra Cheese </label></p>
  <p><label> <input type=checkbox> Onion </label></p>
  <p><label> <input type=checkbox> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900"></label></p>
</form>

The textarea element can be used to provide a free-form text field. In this instance, we are going to use it to provide a space for the customer to give delivery instructions:

<form>
 <p><label>Customer name: <input></label></p>
 <p><label>Telephone: <input type=tel></label></p>
 <p><label>E-mail address: <input type=email></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox> Bacon </label></p>
  <p><label> <input type=checkbox> Extra Cheese </label></p>
  <p><label> <input type=checkbox> Onion </label></p>
  <p><label> <input type=checkbox> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900"></label></p>
 <p><label>Delivery instructions: <textarea></textarea></label></p>
</form>

Finally, to make the form submittable we use the button element:

<form>
 <p><label>Customer name: <input></label></p>
 <p><label>Telephone: <input type=tel></label></p>
 <p><label>E-mail address: <input type=email></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox> Bacon </label></p>
  <p><label> <input type=checkbox> Extra Cheese </label></p>
  <p><label> <input type=checkbox> Onion </label></p>
  <p><label> <input type=checkbox> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900"></label></p>
 <p><label>Delivery instructions: <textarea></textarea></label></p>
 <p><button>Submit order</button><p>
</form>

4.10.1.2 Implementing the server-side processing for a form

This section is non-normative.

The exact details for writing a server-side processor are out of scope for this specification. For the purposes of this introduction, we will assume that the script at https://pizza.example.com/order.cgi is configured to accept submissions using the application/x-www-form-urlencoded format, expecting the following parameters sent in an HTTP POST body:

custname: Customer's name
custtel: Customer's telephone number
custemail: Customer's e-mail address
size: The pizza size, either small, medium, or large
toppings: The topping, specified once for each selected topping, with the allowed values being bacon, cheese, onion, and mushroom
delivery: The requested delivery time
comments: The delivery instructions

4.10.1.3 Configuring a form to communicate with a server

This section is non-normative.

Form submissions are exposed to servers in a variety of ways, most commonly as HTTP GET or POST requests. To specify the exact method used, the method attribute is specified on the form element. This doesn't specify how the form data is encoded, though; to specify that, you use the enctype attribute. You also have to specify the URL of the service that will handle the submitted data, using the action attribute.

For each form control you want submitted, you then have to give a name that will be used to refer to the data in the submission. We already specified the name for the group of radio buttons; the same attribute (name) also specifies the submission name. Radio buttons can be distinguished from each other in the submission by giving them different values, using the value attribute.

Multiple controls can have the same name; for example, here we give all the checkboxes the same name, and the server distinguishes which checkbox was checked by seeing which values are submitted with that name — like the radio buttons, they are also given unique values with the value attribute.

Given the settings in the previous section, this all becomes:

<form method="post"
      enctype="application/x-www-form-urlencoded"
      action="https://pizza.example.com/order.cgi">
 <p><label>Customer name: <input name="custname"></label></p>
 <p><label>Telephone: <input type=tel name="custtel"></label></p>
 <p><label>E-mail address: <input type=email name="custemail"></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size value="small"> Small </label></p>
  <p><label> <input type=radio name=size value="medium"> Medium </label></p>
  <p><label> <input type=radio name=size value="large"> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox name="topping" value="bacon"> Bacon </label></p>
  <p><label> <input type=checkbox name="topping" value="cheese"> Extra Cheese </label></p>
  <p><label> <input type=checkbox name="topping" value="onion"> Onion </label></p>
  <p><label> <input type=checkbox name="topping" value="mushroom"> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900" name="delivery"></label></p>
 <p><label>Delivery instructions: <textarea name="comments"></textarea></label></p>
 <p><button>Submit order</button><p>
</form>

For example, if the customer entered "Denise Lawrence" as their name, "555-321-8642" as their telephone number, did not specify an e-mail address, asked for a medium-sized pizza, selected the Extra Cheese and Mushroom toppings, entered a delivery time of 7pm, and left the delivery instructions text field blank, the user agent would submit the following to the online Web service:

custname=Denise+Lawrence&custtel=555-321-8624&custemail=&size=medium&topping=cheese&topping=mushroom&delivery=19%3A00&comments=

4.10.1.4 Client-side form validation

This section is non-normative.

Forms can be annotated in such a way that the user agent will check the user's input before the form is submitted. The server still has to verify the input is valid (since hostile users can easily bypass the form validation), but it allows the user to avoid the wait incurred by having the server be the sole checker of the user's input.

The simplest annotation is the required attribute, which can be specified on input elements to indicate that the form is not to be submitted until a value is given. By adding this attribute to the customer name and delivery time fields, we allow the user agent to notify the user when the user submits the form without filling in those fields:

<form method="post"
      enctype="application/x-www-form-urlencoded"
      action="https://pizza.example.com/order.cgi">
 <p><label>Customer name: <input name="custname" required></label></p>
 <p><label>Telephone: <input type=tel name="custtel"></label></p>
 <p><label>E-mail address: <input type=email name="custemail"></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size value="small"> Small </label></p>
  <p><label> <input type=radio name=size value="medium"> Medium </label></p>
  <p><label> <input type=radio name=size value="large"> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox name="topping" value="bacon"> Bacon </label></p>
  <p><label> <input type=checkbox name="topping" value="cheese"> Extra Cheese </label></p>
  <p><label> <input type=checkbox name="topping" value="onion"> Onion </label></p>
  <p><label> <input type=checkbox name="topping" value="mushroom"> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900" name="delivery" required></label></p>
 <p><label>Delivery instructions: <textarea name="comments"></textarea></label></p>
 <p><button>Submit order</button><p>
</form>

It is also possible to limit the length of the input, using the maxlength attribute. By adding this to the textarea element, we can limit users to 1000 characters, preventing them from writing huge essays to the busy delivery drivers instead of staying focused and to the point:

<form method="post"
      enctype="application/x-www-form-urlencoded"
      action="https://pizza.example.com/order.cgi">
 <p><label>Customer name: <input name="custname" required></label></p>
 <p><label>Telephone: <input type=tel name="custtel"></label></p>
 <p><label>E-mail address: <input type=email name="custemail"></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size value="small"> Small </label></p>
  <p><label> <input type=radio name=size value="medium"> Medium </label></p>
  <p><label> <input type=radio name=size value="large"> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox name="topping" value="bacon"> Bacon </label></p>
  <p><label> <input type=checkbox name="topping" value="cheese"> Extra Cheese </label></p>
  <p><label> <input type=checkbox name="topping" value="onion"> Onion </label></p>
  <p><label> <input type=checkbox name="topping" value="mushroom"> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900" name="delivery" required></label></p>
 <p><label>Delivery instructions: <textarea name="comments" maxlength=1000></textarea></label></p>
 <p><button>Submit order</button><p>
</form>

4.10.2 Categories

Mostly for historical reasons, elements in this section fall into several overlapping (but subtly different) categories in addition to the usual ones like flow content, phrasing content, and interactive content.

A number of the elements are form-associated elements, which means they can have a form owner and, to expose this, have a form content attribute with a matching form IDL attribute.

The form-associated elements fall into several subcategories:

Listed

Denotes elements that are listed in the form.elements and fieldset.elements APIs.

Labelable

Denotes elements that can be associated with label elements.

Submittable elements

Denotes elements that can be used for constructing the form data set when a form element is submitted.

Resettable elements

Denotes elements that can be affected when a form element is reset.

In addition, some submittable elements can be, depending on their attributes, buttons. The prose below defines when an element is a button. Some buttons are specifically submit buttons.

The object element is also a form-associated element and can, with the use of a suitable plugin, partake in form submission.

4.10.3 The `form` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where flow content is expected.

Content model:

Flow content, but with no form element descendants.

Content attributes:

accept-charset

action

autocomplete

enctype

method

name

novalidate

target

DOM interface:

[OverrideBuiltins]
interface HTMLFormElement : HTMLElement {
           attribute DOMString acceptCharset;
           attribute DOMString action;
           attribute boolean autocomplete;
           attribute DOMString enctype;
           attribute DOMString method;
           attribute DOMString name;
           attribute boolean noValidate;
           attribute DOMString target;

  readonly attribute HTMLFormControlsCollection elements;
  readonly attribute long length;
  caller getter any item(in unsigned long index);
  caller getter any namedItem(in DOMString name);

  void submit();
  void reset();
  boolean checkValidity();

  void dispatchFormInput();
  void dispatchFormChange();
};

The form element represents a collection of form-associated elements, some of which can represent editable values that can be submitted to a server for processing.

The accept-charset attribute gives the character encodings that are to be used for the submission. If specified, the value must be an ordered set of unique space-separated tokens, and each token must be an ASCII case-insensitive match for the preferred MIME name of an ASCII-compatible character encoding. [IANACHARSET]

The name attribute represents the form's name within the forms collection. The value must not be the empty string, and the value must be unique amongst the form elements in the forms collection that it is in, if any.

The autocomplete attribute is an enumerated attribute. The attribute has two states. The on keyword maps to the on state, and the off keyword maps to the off state. The attribute may also be omitted. The missing value default is the on state. The off state indicates that by default, input elements in the form will have their resulting autocompletion state set to off; the on state indicates that by default, input elements in the form will have their resulting autocompletion state set to on.

The action, enctype, method, novalidate, and target attributes are attributes for form submission.

form . elements

Returns an HTMLCollection of the form controls in the form (excluding image buttons for historical reasons).

form . length

Returns the number of form controls in the form (excluding image buttons for historical reasons).

element = form . item(index)

form[index]

form(index)

Returns the indexth element in the form (excluding image buttons for historical reasons).

element = form . namedItem(name)

form[name]

form(name)

Returns the form control in the form with the given ID or name (excluding image buttons for historical reasons).

Once an element has been referenced using a particular name, that name will continue being available as a way to reference that element in this method, even if the element's actual ID or name changes, for as long as the element remains in the Document.

If there are multiple matching items, then a NodeList object containing all those elements is returned.

Returns null if no element with that ID or name could be found.

form . submit()

Submits the form.

form . reset()

Resets the form.

form . checkValidity()

Returns true if the form's controls are all valid; otherwise, returns false.

form . dispatchFormInput()

Dispatches a forminput event at all the form controls.

form . dispatchFormChange()

Dispatches a formchange event at all the form controls.

The autocomplete and name IDL attributes must reflect the respective content attributes of the same name.

The acceptCharset IDL attribute must reflect the accept-charset content attribute.

The elements IDL attribute must return an HTMLFormControlsCollection rooted at the Document node, whose filter matches listed elements whose form owner is the form element, with the exception of input elements whose type attribute is in the Image Button state, which must, for historical reasons, be excluded from this particular collection.

The length IDL attribute must return the number of nodes represented by the elements collection.

The indices of the supported indexed properties at any instant are the indices supported by the object returned by the elements attribute at that instant.

The item(index) method must return the value returned by the method of the same name on the elements collection, when invoked with the same argument.

Each form element has a mapping of names to elements called the past names map. It is used to persist names of controls even when they change names.

The names of the supported named properties are the union of the names currently supported by the object returned by the elements attribute, and the names currently in the past names map.

The namedItem(name) method, when called, must run the following steps:

If name is one of the names of the supported named properties of the object returned by the elements attribute, then run these substeps:
1. Let candidate be the object returned by the namedItem() method on the object returned by the elements attribute when passed the name argument.
2. If candidate is an element, then add a mapping from name to candidate in the form element's past names map, replacing the previous entry with the same name, if any.
3. Return candidate and abort these steps.
Otherwise, name is the name of one of the entries in the form element's past names map: return the object associated with name in that map.

If an element listed in the form element's past names map is removed from the Document, then its entries must be removed from the map.

The submit() method, when invoked, must submit the form element from the form element itself, with the scripted-submit flag set.

The reset() method, when invoked, must run the following steps:

If the form element is marked as locked for reset, then abort these steps.
Mark the form element as locked for reset.
Reset the form element.
Unmark the form element as locked for reset.

If the checkValidity() method is invoked, the user agent must statically validate the constraints of the form element, and return true if the constraint validation return a positive result, and false if it returned a negative result.

If the dispatchFormInput() method is invoked, the user agent must broadcast forminput events from the form element.

If the dispatchFormChange() method is invoked, the user agent must broadcast formchange events from the form element.

This example shows two search forms:

<form action="http://www.google.com/search" method="get">
 <label>Google: <input type="search" name="q"></label> <input type="submit" value="Search...">
</form>
<form action="http://www.bing.com/search" method="get">
 <label>Bing: <input type="search" name="q"></label> <input type="submit" value="Search...">
</form>

4.10.4 The `fieldset` element

Status: Last call for comments

Categories

Listed form-associated element.

Contexts in which this element may be used:

Where flow content is expected.

Content model:

Optionally a legend element, followed by flow content.

Content attributes:

disabled

form

name

DOM interface:

interface HTMLFieldSetElement : HTMLElement {
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
           attribute DOMString name;

  readonly attribute DOMString type;

  readonly attribute HTMLFormControlsCollection elements;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);
};

The fieldset element represents a set of form controls optionally grouped under a common name.

The name of the group is given by the first legend element that is a child of the fieldset element, if any. The remainder of the descendants form the group.

The disabled attribute, when specified, causes all the form control descendants of the fieldset element, excluding those that are descendants of the fieldset element's first legend element child, if any, to be disabled.

The form attribute is used to explicitly associate the fieldset element with its form owner. The name attribute represents the element's name.

fieldset . type: Returns the string "fieldset".
fieldset . elements: Returns an HTMLCollection of the form controls in the element.

The disabled IDL attribute must reflect the content attribute of the same name.

The type IDL attribute must return the string "fieldset".

The elements IDL attribute must return an HTMLFormControlsCollection rooted at the fieldset element, whose filter matches listed elements.

The willValidate, validity, and validationMessage attributes, and the checkValidity() and setCustomValidity() methods, are part of the constraint validation API.

Constraint validation: fieldset elements are always barred from constraint validation.

The following snippet shows a fieldset with a checkbox in the legend that controls whether or not the fieldset is enabled. The contents of the fieldset consist of two required text fields and an optional year/month control.

<fieldset name="clubfields" disabled>
 <legend> <label>
  <input type=checkbox name=club onchange="form.clubfields.disabled = !checked">
  Use Club Card
 </label> </legend>
 <p><label>Name on card: <input name=clubname required></label></p>
 <p><label>Card number: <input name=clubnum required pattern="[-0-9]+"></label></p>
 <p><label>Expiry date: <input name=clubexp type=month></label></p>
</fieldset>

4.10.5 The `legend` element

Status: Last call for comments

Categories

None.

Contexts in which this element may be used:

As the first child of a fieldset element.

Content model:

Content attributes:

DOM interface:

interface HTMLLegendElement : HTMLElement {
  readonly attribute HTMLFormElement form;
};

The legend element represents a caption for the rest of the contents of the legend element's parent fieldset element, if any.

legend . form: Returns the element's form element, if any, or null otherwise.

The form IDL attribute's behavior depends on whether the legend element is in a fieldset element or not. If the legend has a fieldset element as its parent, then the form IDL attribute must return the same value as the form IDL attribute on that fieldset element. Otherwise, it must return null.

4.10.6 The `label` element

Status: Last call for comments

Categories

Form-associated element.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Phrasing content, but with no descendant labelable form-associated elements unless it is the element's labeled control, and no descendant label elements.

Content attributes:

form

for

DOM interface:

interface HTMLLabelElement : HTMLElement {
  readonly attribute HTMLFormElement form;
           attribute DOMString htmlFor;
  readonly attribute HTMLElement control;
};

The label represents a caption in a user interface. The caption can be associated with a specific form control, known as the label element's labeled control, either using for attribute, or by putting the form control inside the label element itself.

Except where otherwise specified by the following rules, a label element has no labeled control.

The for attribute may be specified to indicate a form control with which the caption is to be associated. If the attribute is specified, the attribute's value must be the ID of a labelable form-associated element in the same Document as the label element. If the attribute is specified and there is an element in the Document whose ID is equal to the value of the for attribute, and the first such element is a labelable form-associated element, then that element is the label element's labeled control.

If the for attribute is not specified, but the label element has a labelable form-associated element descendant, then the first such descendant in tree order is the label element's labeled control.

The label element's exact default presentation and behavior, in particular what its activation behavior might be, if anything, should match the platform's label behavior.

For example, on platforms where clicking a checkbox label checks the checkbox, clicking the label in the following snippet could trigger the user agent to run synthetic click activation steps on the input element, as if the element itself had been triggered by the user:

<label><input type=checkbox name=lost> Lost</label>

On other platforms, the behavior might be just to focus the control, or do nothing.

label . control: Returns the form control that is associated with this element.

The form attribute is used to explicitly associate the label element with its form owner.

The htmlFor IDL attribute must reflect the for content attribute.

The control IDL attribute must return the label element's labeled control, if any, or null if there isn't one.

control . labels: Returns a NodeList of all the label elements that the form control is associated with.

Labelable form-associated elements have a NodeList object associated with them that represents the list of label elements, in tree order, whose labeled control is the element in question. The labels IDL attribute of labelable form-associated elements, on getting, must return that NodeList object.

The following example shows three form controls each with a label, two of which have small text showing the right format for users to use.

<p><label>Full name: <input name=fn> <small>Format: First Last</small></label></p>
<p><label>Age: <input name=age type=number min=0></label></p>
<p><label>Post code: <input name=pc> <small>Format: AB12 3CD</small></label></p>

4.10.7 The `input` element

Status: Last call for comments

Categories

If the type attribute is not in the Hidden state: Interactive content.

Listed, labelable, submittable, and resettable form-associated element.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Empty.

Content attributes:

accept

alt

autocomplete

autofocus

checked

disabled

form

formaction

formenctype

formmethod

formnovalidate

formtarget

height

list

max

maxlength

min

multiple

name

pattern

placeholder

readonly

required

size

src

step

type

value

width

DOM interface:

interface HTMLInputElement : HTMLElement {
           attribute DOMString accept;
           attribute DOMString alt;
           attribute boolean autocomplete;
           attribute boolean autofocus;
           attribute boolean defaultChecked;
           attribute boolean checked;
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
  readonly attribute FileList files;
           attribute DOMString formAction;
           attribute DOMString formEnctype;
           attribute DOMString formMethod;
           attribute boolean formNoValidate;
           attribute DOMString formTarget;
           attribute DOMString height;
           attribute boolean indeterminate;
  readonly attribute HTMLElement list;
           attribute DOMString max;
           attribute long maxLength;
           attribute DOMString min;
           attribute boolean multiple;
           attribute DOMString name;
           attribute DOMString pattern;
           attribute DOMString placeholder;
           attribute boolean readOnly;
           attribute boolean required;
           attribute unsigned long size;
           attribute DOMString src;
           attribute DOMString step;
           attribute DOMString type;
           attribute DOMString defaultValue;
           attribute DOMString value;
           attribute Date valueAsDate;
           attribute float valueAsNumber;
  readonly attribute HTMLOptionElement selectedOption;
           attribute DOMString width;

  void stepUp(in optional long n);
  void stepDown(in optional long n);

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);

  readonly attribute NodeList labels;

  void select();
           attribute unsigned long selectionStart;
           attribute unsigned long selectionEnd;
  void setSelectionRange(in unsigned long start, in unsigned long end);
};

The input element represents a typed data field, usually with a form control to allow the user to edit the data.

The type attribute controls the data type (and associated control) of the element. It is an enumerated attribute. The following table lists the keywords and states for the attribute — the keywords in the left column map to the states in the cell in the second column on the same row as the keyword.

Keyword	State	Data type	Control type
`hidden`	Hidden	An arbitrary string	n/a
`text`	Text	Text with no line breaks	Text field
`search`	Search	Text with no line breaks	Search field
`tel`	Telephone	Text with no line breaks	A text field
`url`	URL	An absolute IRI	A text field
`email`	E-mail	An e-mail address or list of e-mail addresses	A text field
`password`	Password	Text with no line breaks (sensitive information)	Text field that obscures data entry
`datetime`	Date and Time	A date and time (year, month, day, hour, minute, second, fraction of a second) with the time zone set to UTC	A date and time control
`date`	Date	A date (year, month, day) with no time zone	A date control
`month`	Month	A date consisting of a year and a month with no time zone	A month control
`week`	Week	A date consisting of a week-year number and a week number with no time zone	A week control
`time`	Time	A time (hour, minute, seconds, fractional seconds) with no time zone	A time control
`datetime-local`	Local Date and Time	A date and time (year, month, day, hour, minute, second, fraction of a second) with no time zone	A date and time control
`number`	Number	A numerical value	A text field or spinner control
`range`	Range	A numerical value, with the extra semantic that the exact value is not important	A slider control or similar
`color`	Color	An sRGB color with 8-bit red, green, and blue components	A color well
`checkbox`	Checkbox	A set of zero or more values from a predefined list	A checkbox
`radio`	Radio Button	An enumerated value	A radio button
`file`	File Upload	Zero or more files each with a MIME type and optionally a file name	A label and a button
`submit`	Submit Button	An enumerated value, with the extra semantic that it must be the last value selected and initiates form submission	A button
`image`	Image Button	A coordinate, relative to a particular image's size, with the extra semantic that it must be the last value selected and initiates form submission	Either a clickable image, or a button
`reset`	Reset Button	n/a	A button
`button`	Button	n/a	A button

The missing value default is the Text state.

Which of the accept, alt, autocomplete, checked, formaction, formenctype, formmethod, formnovalidate, formtarget, height, list, max, maxlength, min, multiple, pattern, placeholder, readonly, required, size, src, step, and width content attributes, the checked, files, valueAsDate, valueAsNumber, list, and selectedOption IDL attributes, the select() method, the selectionStart and selectionEnd IDL attributes, the setSelectionRange() method, the stepUp() and stepDown() methods, and the input and change events apply to an input element depends on the state of its type attribute. The following table is non-normative and summarizes which of those content attributes, IDL attributes, methods, and events apply to each state:

	Hidden	Text, Search, URL, Telephone	E-mail	Password	Date and Time, Date, Month, Week, Time	Local Date and Time, Number	Range	Color	Checkbox, Radio Button	File Upload	Submit Button	Image Button	Reset Button, Button
Content attributes
`accept`	·	·	·	·	·	·	·	·	·	Yes	·	·	·
`alt`	·	·	·	·	·	·	·	·	·	·	·	Yes	·
`autocomplete`	·	Yes	Yes	Yes	Yes	Yes	Yes	Yes	·	·	·	·	·
`checked`	·	·	·	·	·	·	·	·	Yes	·	·	·	·
`formaction`	·	·	·	·	·	·	·	·	·	·	Yes	Yes	·
`formenctype`	·	·	·	·	·	·	·	·	·	·	Yes	Yes	·
`formmethod`	·	·	·	·	·	·	·	·	·	·	Yes	Yes	·
`formnovalidate`	·	·	·	·	·	·	·	·	·	·	Yes	Yes	·
`formtarget`	·	·	·	·	·	·	·	·	·	·	Yes	Yes	·
`height`	·	·	·	·	·	·	·	·	·	·	·	Yes	·
`list`	·	Yes	Yes	·	Yes	Yes	Yes	Yes	·	·	·	·	·
`max`	·	·	·	·	Yes	Yes	Yes	·	·	·	·	·	·
`maxlength`	·	Yes	Yes	Yes	·	·	·	·	·	·	·	·	·
`min`	·	·	·	·	Yes	Yes	Yes	·	·	·	·	·	·
`multiple`	·	·	Yes	·	·	·	·	·	·	Yes	·	·	·
`pattern`	·	Yes	Yes	Yes	·	·	·	·	·	·	·	·	·
`placeholder`	·	Yes	Yes	Yes	·	·	·	·	·	·	·	·	·
`readonly`	·	Yes	Yes	Yes	Yes	Yes	·	·	·	·	·	·	·
`required`	·	Yes	Yes	Yes	Yes	Yes	·	·	Yes	Yes	·	·	·
`size`	·	Yes	Yes	Yes	·	·	·	·	·	·	·	·	·
`src`	·	·	·	·	·	·	·	·	·	·	·	Yes	·
`step`	·	·	·	·	Yes	Yes	Yes	·	·	·	·	·	·
`width`	·	·	·	·	·	·	·	·	·	·	·	Yes	·
IDL attributes and methods
`checked`	·	·	·	·	·	·	·	·	Yes	·	·	·	·
`files`	·	·	·	·	·	·	·	·	·	Yes	·	·	·
`value`	default	value	value	value	value	value	value	value	default/on	filename	default	default	default
`valueAsDate`	·	·	·	·	Yes	·	·	·	·	·	·	·	·
`valueAsNumber`	·	·	·	·	Yes	Yes	Yes	·	·	·	·	·	·
`list`	·	Yes	Yes	·	Yes	Yes	Yes	Yes	·	·	·	·	·
`selectedOption`	·	Yes	Yes	·	Yes	Yes	Yes	Yes	·	·	·	·	·
`select()`	·	Yes	Yes	Yes	·	·	·	·	·	·	·	·	·
`selectionStart`	·	Yes	Yes	Yes	·	·	·	·	·	·	·	·	·
`selectionEnd`	·	Yes	Yes	Yes	·	·	·	·	·	·	·	·	·
`setSelectionRange()`	·	Yes	Yes	Yes	·	·	·	·	·	·	·	·	·
`stepDown()`	·	·	·	·	Yes	Yes	Yes	·	·	·	·	·	·
`stepUp()`	·	·	·	·	Yes	Yes	Yes	·	·	·	·	·	·
Events
`input` event	·	Yes	Yes	Yes	Yes	Yes	Yes	Yes	·	·	·	·	·
`change` event	·	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	·	·	·

When an input element's type attribute changes state, and when the element is first created, the element's rendering and behavior must change to the new state's accordingly and the value sanitization algorithm, if one is defined for the type attribute's new state, must be invoked.

Each input element has a value, which is exposed by the value IDL attribute. Some states define an algorithm to convert a string to a number, an algorithm to convert a number to a string, an algorithm to convert a string to a Date object, and an algorithm to convert a Date object to a string, which are used by max, min, step, valueAsDate, valueAsNumber, stepDown(), and stepUp().

Each input element has a boolean dirty value flag. When it is true, the element is said to have a dirty value. The dirty value flag must be initially set to false when the element is created, and must be set to true whenever the user interacts with the control in a way that changes the value.

The value content attribute gives the default value of the input element. When the value content attribute is added, set, or removed, if the control does not have a dirty value, the user agent must set the value of the element to the value of the value content attribute, if there is one, or the empty string otherwise, and then run the current value sanitization algorithm, if one is defined.

Each input element has a checkedness, which is exposed by the checked IDL attribute.

Each input element has a boolean dirty checkedness flag. When it is true, the element is said to have a dirty checkedness. The dirty checkedness flag must be initially set to false when the element is created, and must be set to true whenever the user interacts with the control in a way that changes the checkedness.

The checked content attribute is a boolean attribute that gives the default checkedness of the input element. When the checked content attribute is added, if the control does not have dirty checkedness, the user agent must set the checkedness of the element to true; when the checked content attribute is removed, if the control does not have dirty checkedness, the user agent must set the checkedness of the element to false.

The reset algorithm for input elements is to set the dirty value flag and dirty checkedness flag back to false, set the value of the element to the value of the value content attribute, if there is one, or the empty string otherwise, set the checkedness of the element to true if the element has a checked content attribute and false if it does not, and then invoke the value sanitization algorithm, if the type attribute's current state defines one.

Each input element is either mutable or immutable. Except where otherwise specified, an input element is always mutable. Similarly, except where otherwise specified, the user agent should not allow the user to modify the element's value or checkedness.

When an input element is disabled, it is immutable.

When an input element does not have a Document node as one of its ancestors (i.e. when it is not in the document), it is immutable.

The readonly attribute can also in some cases (e.g. for the Date state, but not the Checkbox state) make an input element immutable.

When an input element is cloned, the element's value, dirty value flag, checkedness, and dirty checkedness flag must be propagated to the clone when it is created.

The form attribute is used to explicitly associate the input element with its form owner. The name attribute represents the element's name. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The autofocus attribute controls focus.

The indeterminate IDL attribute must initially be set to false. On getting, it must return the last value it was set to. On setting, it must be set to the new value. It has no effect except for changing the appearance of checkbox controls.

The accept, alt, autocomplete, max, min, multiple, pattern, placeholder, required, size, src, step, and type IDL attributes must reflect the respective content attributes of the same name. The maxLength IDL attribute must reflect the maxlength content attribute, limited to only non-negative numbers. The readOnly IDL attribute must reflect the readonly content attribute. The defaultChecked IDL attribute must reflect the checked content attribute. The defaultValue IDL attribute must reflect the value content attribute.

The willValidate, validity, and validationMessage attributes, and the checkValidity() and setCustomValidity() methods, are part of the constraint validation API. The labels attribute provides a list of the element's labels. The select(), selectionStart, selectionEnd, and setSelectionRange() methods and attributes expose the element's text selection.

4.10.7.1 States of the `type` attribute

Status: Last call for comments

4.10.7.1.1 Hidden state

Status: Last call for comments

When an input element's type attribute is in the Hidden state, the rules in this section apply.

The input element represents a value that is not intended to be examined or manipulated by the user.

Constraint validation: If an input element's type attribute is in the Hidden state, it is barred from constraint validation.

If the name attribute is present and has a value that is a case-sensitive match for the string "_charset_", then the element's value attribute must be omitted.

The value IDL attribute applies to this element and is in mode default.

The following content attributes must not be specified and do not apply to the element: accept, alt, autocomplete, checked, formaction, formenctype, formmethod, formnovalidate, formtarget, height, list, max, maxlength, min, multiple, pattern, placeholder, readonly, required, size, src, step, and width.

The following IDL attributes and methods do not apply to the element: checked, files, list, selectedOption, selectionStart, selectionEnd, valueAsDate, and valueAsNumber IDL attributes; select(), setSelectionRange(), stepDown(), and stepUp() methods.

The input and change events do not apply.

4.10.7.1.2 Text state and Search state

Status: Last call for comments

When an input element's type attribute is in the Text state or the Search state, the rules in this section apply.

The input element represents a one line plain text edit control for the element's value.

The difference between the Text state and the Search state is primarily stylistic: on platforms where search fields are distinguished from regular text fields, the Search state might result in an appearance consistent with the platform's search fields rather than appearing like a regular text field.

If the element is mutable, its value should be editable by the user. User agents must not allow users to insert U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters into the element's value.

The value attribute, if specified, must have a value that contains no U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters.

The value sanitization algorithm is as follows: Strip line breaks from the value.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, maxlength, pattern, placeholder, readonly, required, and size content attributes; list, selectedOption, selectionStart, selectionEnd, and value IDL attributes; select() and setSelectionRange() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following content attributes must not be specified and do not apply to the element: accept, alt, checked, formaction, formenctype, formmethod, formnovalidate, formtarget, height, max, min, multiple, src, step, and width.

The following IDL attributes and methods do not apply to the element: checked, files, valueAsDate, and valueAsNumber IDL attributes; stepDown() and stepUp() methods.

4.10.7.1.3 Telephone state

Status: Last call for comments

When an input element's type attribute is in the Telephone state, the rules in this section apply.

The input element represents a control for editing a telephone number given in the element's value.

If the element is mutable, its value should be editable by the user. User agents may change the punctuation of values that the user enters. User agents must not allow users to insert U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters into the element's value.

The value attribute, if specified, must have a value that contains no U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters.

The value sanitization algorithm is as follows: Strip line breaks from the value.

Unlike the URL and E-mail types, the Telephone type does not enforce a particular syntax. This is intentional; in practice, telephone number fields tend to be free-form fields, because there are a wide variety of valid phone numbers. Systems that need to enforce a particular format are encouraged to use the setCustomValidity() method to hook into the client-side validation mechanism.

The value IDL attribute is in mode value.

The input and change events apply.

The following IDL attributes and methods do not apply to the element: checked, files, valueAsDate, and valueAsNumber IDL attributes; stepDown() and stepUp() methods.

4.10.7.1.4 URL state

Status: Last call for comments

When an input element's type attribute is in the URL state, the rules in this section apply.

The input element represents a control for editing a single absolute URL given in the element's value.

If the element is mutable, the user agent should allow the user to change the URL represented by its value. User agents may allow the user to set the value to a string that is not a valid absolute URL, but may also or instead automatically escape characters entered by the user so that the value is always a valid absolute URL (even if that isn't the actual value seen and edited by the user in the interface). User agents should allow the user to set the value to the empty string. User agents must not allow users to insert U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters into the value.

The value attribute, if specified, must have a value that is a valid absolute URL.

The value sanitization algorithm is as follows: Strip line breaks from the value.

Constraint validation: While the value of the element is not a valid absolute URL, the element is suffering from a type mismatch.

The value IDL attribute is in mode value.

The input and change events apply.

The following IDL attributes and methods do not apply to the element: checked, files, valueAsDate, and valueAsNumber IDL attributes; stepDown() and stepUp() methods.

If a document contained the following markup:

<input type="url" name="location" list="urls">
<datalist id="urls">
 <option label="MIME: Format of Internet Message Bodies" value="http://www.ietf.org/rfc/rfc2045">
 <option label="HTML 4.01 Specification" value="http://www.w3.org/TR/html4/">
 <option label="Form Controls" value="http://www.w3.org/TR/xforms/slice8.html#ui-commonelems-hint">
 <option label="Scalable Vector Graphics (SVG) 1.1 Specification" value="http://www.w3.org/TR/SVG/">
 <option label="Feature Sets - SVG 1.1 - 20030114" value="http://www.w3.org/TR/SVG/feature.html">
 <option label="The Single UNIX Specification, Version 3" value="http://www.unix-systems.org/version3/">
</datalist>

...and the user had typed "www.w3", and the user agent had also found that the user had visited http://www.w3.org/Consortium/#membership and http://www.w3.org/TR/XForms/ in the recent past, then the rendering might look like this:

A text box with an icon on the left followed by the text "www.w3" and a cursor, with a drop down button on the right hand side; with, below, a drop down box containing a list of six URIs on the left, with the first four having grayed out labels on the right; and a scroll bar to the right of the drow down box, indicating further values are available.

The first four URIs in this sample consist of the four URIs in the author-specified list that match the text the user has entered, sorted lexically. Note how the UA is using the knowledge that the values are URIs to allow the user to omit the scheme part and perform intelligent matching on the domain name.

The last two URIs (and probably many more, given the scrollbar's indications of more values being available) are the matches from the user agent's session history data. This data is not made available to the page DOM. In this particular case, the UA has no titles to provide for those values.

4.10.7.1.5 E-mail state

Status: Last call for comments

When an input element's type attribute is in the E-mail state, the rules in this section apply.

The input element represents a control for editing a list of e-mail addresses given in the element's value.

If the element is mutable, the user agent should allow the user to change the e-mail addresses represented by its value. If the multiple attribute is specified, then the user agent should allow the user to select or provide multiple addresses; otherwise, the user agent should act in a manner consistent with expecting the user to provide a single e-mail address. User agents may allow the user to set the value to a string that is not a valid e-mail address list. User agents should allow the user to set the value to the empty string. User agents must not allow users to insert U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters into the value. User agents may transform the value for display and editing (e.g. converting punycode in the value to IDN in the display and vice versa).

If the multiple attribute is specified on the element, then the value attribute, if specified, must have a value that is a valid e-mail address list; otherwise, the value attribute, if specified, must have a value that is a single valid e-mail address.

The value sanitization algorithm is as follows: Strip line breaks from the value.

Constraint validation: If the multiple attribute is specified on the element, then, while the value of the element is not a valid e-mail address list, the element is suffering from a type mismatch; otherwise, while the value of the element is not a single valid e-mail address, the element is suffering from a type mismatch.

A valid e-mail address list is a set of comma-separated tokens, where each token is itself a valid e-mail address. To obtain the list of tokens from a valid e-mail address list, the user agent must split the string on commas.

A valid e-mail address is a string that matches the ABNF production 1*( atext / "." ) "@" ldh-str 1*( "." ldh-str ) where atext is defined in RFC 5322 section 3.2.3, and ldh-str is defined in RFC 1034 section 3.5. [ABNF] [RFC5322] [RFC1034]

This requirement is a willful violation of RFC 5322, which defines a syntax for e-mail addresses that is simultaneously too strict (before the "@" character), too vague (after the "@" character), and too lax (allowing comments, white space characters, and quoted strings in manners unfamiliar to most users) to be of practical use here.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, maxlength, multiple, pattern, placeholder, readonly, required, and size content attributes; list, selectedOption, selectionStart, selectionEnd, and value IDL attributes; select() and setSelectionRange() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following IDL attributes and methods do not apply to the element: checked, files, valueAsDate, and valueAsNumber IDL attributes; stepDown() and stepUp() methods.

4.10.7.1.6 Password state

Status: Last call for comments

When an input element's type attribute is in the Password state, the rules in this section apply.

The input element represents a one line plain text edit control for the element's value. The user agent should obscure the value so that people other than the user cannot see it.

If the element is mutable, its value should be editable by the user. User agents must not allow users to insert U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters into the value.

The value attribute, if specified, must have a value that contains no U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters.

The value sanitization algorithm is as follows: Strip line breaks from the value.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, maxlength, pattern, placeholder, readonly, required, and size content attributes; selectionStart, selectionEnd, and value IDL attributes; select(), and setSelectionRange() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following content attributes must not be specified and do not apply to the element: accept, alt, checked, formaction, formenctype, formmethod, formnovalidate, formtarget, height, list, max, min, multiple, src, step, and width.

The following IDL attributes and methods do not apply to the element: checked, files, list, selectedOption, valueAsDate, and valueAsNumber IDL attributes; stepDown() and stepUp() methods.

4.10.7.1.7 Date and Time state

Status: Last call for comments

When an input element's type attribute is in the Date and Time state, the rules in this section apply.

The input element represents a control for setting the element's value to a string representing a specific global date and time. User agents may display the date and time in whatever time zone is appropriate for the user.

If the element is mutable, the user agent should allow the user to change the global date and time represented by its value, as obtained by parsing a global date and time from it. User agents must not allow the user to set the value to a string that is not a valid global date and time string expressed in UTC, though user agents may allow the user to set and view the time in another time zone and silently translate the time to and from the UTC time zone in the value. If the user agent provides a user interface for selecting a global date and time, then the value must be set to a valid global date and time string expressed in UTC representing the user's selection. User agents should allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid global date and time string.

The value sanitization algorithm is as follows: If the value of the element is a valid global date and time string, then adjust the time so that the value represents the same point in time but expressed in the UTC time zone, otherwise, set it to the empty string instead.

The min attribute, if specified, must have a value that is a valid global date and time string. The max attribute, if specified, must have a value that is a valid global date and time string.

The step attribute is expressed in seconds. The step scale factor is 1000 (which converts the seconds to milliseconds, as used in the other algorithms). The default step is 60 seconds.

When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest global date and time for which the element would not suffer from a step mismatch.

The algorithm to convert a string to a number, given a string input, is as follows: If parsing a global date and time from input results in an error, then return an error; otherwise, return the number of milliseconds elapsed from midnight UTC on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0Z") to the parsed global date and time, ignoring leap seconds.

The algorithm to convert a number to a string, given a number input, is as follows: Return a valid global date and time string expressed in UTC that represents the global date and time that is input milliseconds after midnight UTC on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0Z").

The algorithm to convert a string to a Date object, given a string input, is as follows: If parsing a global date and time from input results in an error, then return an error; otherwise, return a Date object representing the parsed global date and time, expressed in UTC.

The algorithm to convert a Date object to a string, given a Date object input, is as follows: Return a valid global date and time string expressed in UTC that represents the global date and time that is represented by input.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, max, min, readonly, required, and step content attributes; list, value, valueAsDate, valueAsNumber, and selectedOption IDL attributes; stepDown() and stepUp() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following IDL attributes and methods do not apply to the element: checked, files, selectionStart, and selectionEnd IDL attributes; select() and setSelectionRange() methods.

The following fragment shows part of a calendar application. A user can specify a date and time for a meeting (in his local time zone, probably, though the user agent can allow the user to change that), and since the submitted data includes the time-zone offset, the application can ensure that the meeting is shown at the correct time regardless of the time zones used by all the participants.

<fieldset>
 <legend>Add Meeting</legend>
 <p><label>Meeting name: <input type=text name="meeting.label"></label>
 <p><label>Meeting time: <input type=datetime name="meeting.start"></label>
</fieldset>

Had the application used the datetime-local type instead, the calendar application would have also had to explicitly determine which time zone the user intended.

4.10.7.1.8 Date state

Status: Last call for comments

When an input element's type attribute is in the Date state, the rules in this section apply.

The input element represents a control for setting the element's value to a string representing a specific date.

If the element is mutable, the user agent should allow the user to change the date represented by its value, as obtained by parsing a date from it. User agents must not allow the user to set the value to a string that is not a valid date string. If the user agent provides a user interface for selecting a date, then the value must be set to a valid date string representing the user's selection. User agents should allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid date string.

The value sanitization algorithm is as follows: If the value of the element is not a valid date string, then set it to the empty string instead.

The min attribute, if specified, must have a value that is a valid date string. The max attribute, if specified, must have a value that is a valid date string.

The step attribute is expressed in days. The step scale factor is 86,400,000 (which converts the days to milliseconds, as used in the other algorithms). The default step is 1 day.

When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest date for which the element would not suffer from a step mismatch.

The algorithm to convert a string to a number, given a string input, is as follows: If parsing a date from input results in an error, then return an error; otherwise, return the number of milliseconds elapsed from midnight UTC on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0Z") to midnight UTC on the morning of the parsed date, ignoring leap seconds.

The algorithm to convert a number to a string, given a number input, is as follows: Return a valid date string that represents the date that, in UTC, is current input milliseconds after midnight UTC on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0Z").

The algorithm to convert a string to a Date object, given a string input, is as follows: If parsing a date from input results in an error, then return an error; otherwise, return a Date object representing midnight UTC on the morning of the parsed date.

The algorithm to convert a Date object to a string, given a Date object input, is as follows: Return a valid date string that represents the date current at the time represented by input in the UTC time zone.

The value IDL attribute is in mode value.

The input and change events apply.

The following IDL attributes and methods do not apply to the element: checked, selectionStart, and selectionEnd IDL attributes; select() and setSelectionRange() methods.

4.10.7.1.9 Month state

Status: Last call for comments

When an input element's type attribute is in the Month state, the rules in this section apply.

The input element represents a control for setting the element's value to a string representing a specific month.

If the element is mutable, the user agent should allow the user to change the month represented by its value, as obtained by parsing a month from it. User agents must not allow the user to set the value to a string that is not a valid month string. If the user agent provides a user interface for selecting a month, then the value must be set to a valid month string representing the user's selection. User agents should allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid month string.

The value sanitization algorithm is as follows: If the value of the element is not a valid month string, then set it to the empty string instead.

The min attribute, if specified, must have a value that is a valid month string. The max attribute, if specified, must have a value that is a valid month string.

The step attribute is expressed in months. The step scale factor is 1 (there is no conversion needed as the algorithms use months). The default step is 1 month.

When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest month for which the element would not suffer from a step mismatch.

The algorithm to convert a string to a number, given a string input, is as follows: If parsing a month from input results in an error, then return an error; otherwise, return the number of months between January 1970 and the parsed month.

The algorithm to convert a number to a string, given a number input, is as follows: Return a valid month string that represents the month that has input months between it and January 1970.

The algorithm to convert a string to a Date object, given a string input, is as follows: If parsing a month from input results in an error, then return an error; otherwise, return a Date object representing midnight UTC on the morning of the first day of the parsed month.

The algorithm to convert a Date object to a string, given a Date object input, is as follows: Return a valid month string that represents the month current at the time represented by input in the UTC time zone.

The value IDL attribute is in mode value.

The input and change events apply.

The following IDL attributes and methods do not apply to the element: checked, files, selectionStart, and selectionEnd IDL attributes; select() and setSelectionRange() methods.

4.10.7.1.10 Week state

Status: Last call for comments

When an input element's type attribute is in the Week state, the rules in this section apply.

The input element represents a control for setting the element's value to a string representing a specific week.

If the element is mutable, the user agent should allow the user to change the week represented by its value, as obtained by parsing a week from it. User agents must not allow the user to set the value to a string that is not a valid week string. If the user agent provides a user interface for selecting a week, then the value must be set to a valid week string representing the user's selection. User agents should allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid week string.

The value sanitization algorithm is as follows: If the value of the element is not a valid week string, then set it to the empty string instead.

The min attribute, if specified, must have a value that is a valid week string. The max attribute, if specified, must have a value that is a valid week string.

The step attribute is expressed in weeks. The step scale factor is 604,800,000 (which converts the weeks to milliseconds, as used in the other algorithms). The default step is 1 week.

When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest week for which the element would not suffer from a step mismatch.

The algorithm to convert a string to a number, given a string input, is as follows: If parsing a week string from input results in an error, then return an error; otherwise, return the number of milliseconds elapsed from midnight UTC on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0Z") to midnight UTC on the morning of the Monday of the parsed week, ignoring leap seconds.

The algorithm to convert a number to a string, given a number input, is as follows: Return a valid week string that represents the week that, in UTC, is current input milliseconds after midnight UTC on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0Z").

The algorithm to convert a string to a Date object, given a string input, is as follows: If parsing a week from input results in an error, then return an error; otherwise, return a Date object representing midnight UTC on the morning of the Monday of the parsed week.

The algorithm to convert a Date object to a string, given a Date object input, is as follows: Return a valid week string that represents the week current at the time represented by input in the UTC time zone.

The value IDL attribute is in mode value.

The input and change events apply.

The following IDL attributes and methods do not apply to the element: checked, files, selectionStart, and selectionEnd IDL attributes; select() and setSelectionRange() methods.

4.10.7.1.11 Time state

Status: Last call for comments

When an input element's type attribute is in the Time state, the rules in this section apply.

The input element represents a control for setting the element's value to a string representing a specific time.

If the element is mutable, the user agent should allow the user to change the time represented by its value, as obtained by parsing a time from it. User agents must not allow the user to set the value to a string that is not a valid time string. If the user agent provides a user interface for selecting a time, then the value must be set to a valid time string representing the user's selection. User agents should allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid time string.

The value sanitization algorithm is as follows: If the value of the element is not a valid time string, then set it to the empty string instead.

The min attribute, if specified, must have a value that is a valid time string. The max attribute, if specified, must have a value that is a valid time string.

The step attribute is expressed in seconds. The step scale factor is 1000 (which converts the seconds to milliseconds, as used in the other algorithms). The default step is 60 seconds.

When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest time for which the element would not suffer from a step mismatch.

The algorithm to convert a string to a number, given a string input, is as follows: If parsing a time from input results in an error, then return an error; otherwise, return the number of milliseconds elapsed from midnight to the parsed time on a day with no time changes.

The algorithm to convert a number to a string, given a number input, is as follows: Return a valid time string that represents the time that is input milliseconds after midnight on a day with no time changes.

The algorithm to convert a string to a Date object, given a string input, is as follows: If parsing a time from input results in an error, then return an error; otherwise, return a Date object representing the parsed time in UTC on 1970-01-01.

The algorithm to convert a Date object to a string, given a Date object input, is as follows: Return a valid time string that represents the UTC time component that is represented by input.

The value IDL attribute is in mode value.

The input and change events apply.

The following IDL attributes and methods do not apply to the element: checked, files, selectionStart, and selectionEnd IDL attributes; select() and setSelectionRange() methods.

4.10.7.1.12 Local Date and Time state

Status: Last call for comments

When an input element's type attribute is in the Local Date and Time state, the rules in this section apply.

The input element represents a control for setting the element's value to a string representing a local date and time, with no time-zone offset information.

If the element is mutable, the user agent should allow the user to change the date and time represented by its value, as obtained by parsing a date and time from it. User agents must not allow the user to set the value to a string that is not a valid local date and time string. If the user agent provides a user interface for selecting a local date and time, then the value must be set to a valid local date and time string representing the user's selection. User agents should allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid local date and time string.

The value sanitization algorithm is as follows: If the value of the element is not a valid local date and time string, then set it to the empty string instead.

The min attribute, if specified, must have a value that is a valid local date and time string. The max attribute, if specified, must have a value that is a valid local date and time string.

The step attribute is expressed in seconds. The step scale factor is 1000 (which converts the seconds to milliseconds, as used in the other algorithms). The default step is 60 seconds.

When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest local date and time for which the element would not suffer from a step mismatch.

The algorithm to convert a string to a number, given a string input, is as follows: If parsing a date and time from input results in an error, then return an error; otherwise, return the number of milliseconds elapsed from midnight on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0") to the parsed local date and time, ignoring leap seconds.

The algorithm to convert a number to a string, given a number input, is as follows: Return a valid local date and time string that represents the date and time that is input milliseconds after midnight on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0").

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, max, min, readonly, required, and step content attributes; list, value, valueAsNumber, and selectedOption IDL attributes; stepDown() and stepUp() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following IDL attributes and methods do not apply to the element: checked, files, selectionStart, selectionEnd, and valueAsDate IDL attributes; select() and setSelectionRange() methods.

The following example shows part of a flight booking application. The application uses an input element with its type attribute set to datetime-local, and it then interprets the given date and time in the time zone of the selected airport.

<fieldset>
 <legend>Destination</legend>
 <p><label>Airport: <input type=text name=to list=airports></label></p>
 <p><label>Departure time: <input type=datetime-local name=totime step=3600></label></p>
</fieldset>
<datalist id=airports>
 <option value=ATL label="Atlanta">
 <option value=MEM label="Memphis">
 <option value=LHR label="London Heathrow">
 <option value=LAX label="Los Angeles">
 <option value=FRA label="Frankfurt">
</datalist>

If the application instead used the datetime type, then the user would have to work out the time-zone conversions himself, which is clearly not a good user experience!

4.10.7.1.13 Number state

Status: Last call for comments

When an input element's type attribute is in the Number state, the rules in this section apply.

The input element represents a control for setting the element's value to a string representing a number.

If the element is mutable, the user agent should allow the user to change the number represented by its value, as obtained from applying the rules for parsing floating point number values to it. User agents must not allow the user to set the value to a string that is not a valid floating point number. If the user agent provides a user interface for selecting a number, then the value must be set to the best representation of the number representing the user's selection as a floating point number. User agents should allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid floating point number.

The value sanitization algorithm is as follows: If the value of the element is not a valid floating point number, then set it to the empty string instead.

The min attribute, if specified, must have a value that is a valid floating point number. The max attribute, if specified, must have a value that is a valid floating point number.

The step scale factor is 1. The default step is 1 (allowing only integers, unless the min attribute has a non-integer value).

When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest number for which the element would not suffer from a step mismatch.

The algorithm to convert a string to a number, given a string input, is as follows: If applying the rules for parsing floating point number values to input results in an error, then return an error; otherwise, return the resulting number.

The algorithm to convert a number to a string, given a number input, is as follows: Return a valid floating point number that represents input.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, max, min, readonly, required, and step content attributes; list, value, valueAsNumber, and selectedOption IDL attributes; stepDown() and stepUp() methods.

The value IDL attribute is in mode value.

The input and change events apply.

4.10.7.1.14 Range state

Status: Last call for comments

When an input element's type attribute is in the Range state, the rules in this section apply.

The input element represents a control for setting the element's value to a string representing a number, but with the caveat that the exact value is not important, letting UAs provide a simpler interface than they do for the Number state.

In this state, the range and step constraints are enforced even during user input, and there is no way to set the value to the empty string.

If the element is mutable, the user agent should allow the user to change the number represented by its value, as obtained from applying the rules for parsing floating point number values to it. User agents must not allow the user to set the value to a string that is not a valid floating point number. If the user agent provides a user interface for selecting a number, then the value must be set to a best representation of the number representing the user's selection as a floating point number. User agents must not allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid floating point number.

The value sanitization algorithm is as follows: If the value of the element is not a valid floating point number, then set it to a valid floating point number that represents the default value.

The min attribute, if specified, must have a value that is a valid floating point number. The default minimum is 0. The max attribute, if specified, must have a value that is a valid floating point number. The default maximum is 100.

The default value is the minimum plus half the difference between the minimum and the maximum, unless the maximum is less than the minimum, in which case the default value is the minimum.

When the element is suffering from an underflow, the user agent must set the element's value to a valid floating point number that represents the minimum.

When the element is suffering from an overflow, if the maximum is not less than the minimum, the user agent must set the element's value to a valid floating point number that represents the maximum.

The step scale factor is 1. The default step is 1 (allowing only integers, unless the min attribute has a non-integer value).

When the element is suffering from a step mismatch, the user agent must round the element's value to the nearest number for which the element would not suffer from a step mismatch, and which is greater than or equal to the minimum, and, if the maximum is not less than the minimum, which is less than or equal to the maximum.

The algorithm to convert a number to a string, given a number input, is as follows: Return a valid floating point number that represents input.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, max, min, and step content attributes; list, value, valueAsNumber, and selectedOption IDL attributes; stepDown() and stepUp() methods.

The value IDL attribute is in mode value.

The input and change events apply.

Here is an example of a range control using an autocomplete list with the list attribute. This could be useful if there are values along the full range of the control that are especially important, such as preconfigured light levels or typical speed limits in a range control used as a speed control. The following markup fragment:

<input type="range" min="-100" max="100" value="0" step="10" name="power" list="powers">
<datalist id="powers">
 <option value="0">
 <option value="-30">
 <option value="30">
 <option value="+50">
</datalist>

...with the following style sheet applied:

input { height: 75px; width: 49px; background: #D5CCBB; color: black; }

...might render as:

A vertical slider control whose primary colour is black and whose background colour is beige, with the slider having five tick marks, one long one at each extremity, and three short ones clustered around the midpoint.

Note how the UA determined the orientation of the control from the ratio of the style-sheet-specified height and width properties. The colours were similiarly derived from the style sheet. The tick marks, however, were derived from the markup. In particular, the step attribute has not affected the placement of tick marks, the UA deciding to only use the author-specified completion values and then adding longer tick marks at the extremes.

Note also how the invalid value +50 was completely ignored.

For another example, consider the following markup fragment:

<input name=x type=range min=100 max=700 step=9.09090909 value=509.090909>

A user agent could display in a variety of ways, for instance:

As a dial.

Or, alternatively, for instance:

As a long horizontal slider with tick marks.

The user agent could pick which one to display based on the dimensions given in the style sheet. This would allow it to maintain the same resolution for the tick marks, despite the differences in width.

4.10.7.1.15 Color state

Status: Last call for comments

When an input element's type attribute is in the Color state, the rules in this section apply.

The input element represents a color well control, for setting the element's value to a string representing a simple color.

In this state, there is always a color picked, and there is no way to set the value to the empty string.

If the element is mutable, the user agent should allow the user to change the color represented by its value, as obtained from applying the rules for parsing simple color values to it. User agents must not allow the user to set the value to a string that is not a valid lowercase simple color. If the user agent provides a user interface for selecting a color, then the value must be set to the result of using the rules for serializing simple color values to the user's selection. User agents must not allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid simple color.

The value sanitization algorithm is as follows: If the value of the element is a valid simple color, then set it to the value of the element converted to ASCII lowercase; otherwise, set it to the string "#000000".

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete and list content attributes; list, value, and selectedOption IDL attributes.

The value IDL attribute is in mode value.

The input and change events apply.

The following IDL attributes and methods do not apply to the element: checked, files, selectionStart, selectionEnd, valueAsDate, and valueAsNumber IDL attributes; select(), setSelectionRange(), stepDown(), and stepUp() methods.

4.10.7.1.16 Checkbox state

Status: Last call for comments

When an input element's type attribute is in the Checkbox state, the rules in this section apply.

The input element represents a two-state control that represents the element's checkedness state. If the element's checkedness state is true, the control represents a positive selection, and if it is false, a negative selection. If the element's indeterminate IDL attribute is set to true, then the control's selection should be obscured as if the control was in a third, indeterminate, state.

The control is never a true tri-state control, even if the element's indeterminate IDL attribute is set to true. The indeterminate IDL attribute only gives the appearance of a third state.

If the element is mutable, then: The pre-click activation steps consist of setting the element's checkedness to its opposite value (i.e. true if it is false, false if it is true), and of setting the element's indeterminate IDL attribute to false. The canceled activation steps consist of setting the checkedness and the element's indeterminate IDL attribute back to the values they had before the pre-click activation steps were run. The activation behavior is to fire a simple event that bubbles named change at the element, then broadcast formchange events at the element's form owner.

Constraint validation: If the element is required and its checkedness is false, then the element is suffering from being missing.

input . indeterminate [ = value ]: When set, overrides the rendering of checkbox controls so that the current value is not visible.

The following common input element content attributes and IDL attributes apply to the element: checked, and required content attributes; checked and value IDL attributes.

The value IDL attribute is in mode default/on.

The change event applies.

The following content attributes must not be specified and do not apply to the element: accept, alt, autocomplete, formaction, formenctype, formmethod, formnovalidate, formtarget, height, list, max, maxlength, min, multiple, pattern, placeholder, readonly, size, src, step, and width.

The following IDL attributes and methods do not apply to the element: files, list, selectedOption, selectionStart, selectionEnd, valueAsDate, and valueAsNumber IDL attributes; select(), setSelectionRange(), stepDown(), and stepUp() methods.

The input event does not apply.

4.10.7.1.17 Radio Button state

Status: Last call for comments

When an input element's type attribute is in the Radio Button state, the rules in this section apply.

The input element represents a control that, when used in conjunction with other input elements, forms a radio button group in which only one control can have its checkedness state set to true. If the element's checkedness state is true, the control represents the selected control in the group, and if it is false, it indicates a control in the group that is not selected.

The radio button group that contains an input element a also contains all the other input elements b that fulfill all of the following conditions:

The input element b's type attribute is in the Radio Button state.
Either a and b have the same form owner, or they both have no form owner.
They both have a name attribute, and the value of a's name attribute is a compatibility caseless match for the value of b's name attribute.

A document must not contain an input element whose radio button group contains only that element.

When any of the following events occur, if the element's checkedness state is true after the event, the checkedness state of all the other elements in the same radio button group must be set to false:

The element's checkedness state is set to true (for whatever reason).
The element's name attribute is added, removed, or changes value.
The element's form owner changes.

If the element is mutable, then: The pre-click activation steps consist of setting the element's checkedness to true. The canceled activation steps consist of setting the element's checkedness to false. The activation behavior is to fire a simple event that bubbles named change at the element, then broadcast formchange events at the element's form owner.

Constraint validation: If the element is required and all of the input elements in the radio button group have a checkedness that is false, then the element is suffering from being missing.

If none of the radio buttons in a radio button group are checked when they are inserted into the document, then they will all be initially unchecked in the interface, until such time as one of them is checked (either by the user or by script).

The following common input element content attributes and IDL attributes apply to the element: checked and required content attributes; checked and value IDL attributes.

The value IDL attribute is in mode default/on.

The change event applies.

The input event does not apply.

4.10.7.1.18 File Upload state

Status: Last call for comments

When an input element's type attribute is in the File Upload state, the rules in this section apply.

The input element represents a list of selected files, each file consisting of a file name, a file type, and a file body (the contents of the file).

If the element is mutable, the user agent should allow the user to change the files on the list, e.g. adding or removing files. Files can be from the filesystem or created on the fly, e.g. a picture taken from a camera connected to the user's device.

Constraint validation: If the element is required and the list of selected files is empty, then the element is suffering from being missing.

Unless the multiple attribute is set, there must be no more than one file in the list of selected files.

The accept attribute may be specified to provide user agents with a hint of what file types the server will be able to accept.

If specified, the attribute must consist of a set of comma-separated tokens, each of which must be an ASCII case-insensitive match for one of the following:

The string audio/*: Indicates that sound files are accepted.
The string video/*: Indicates that video files are accepted.
The string image/*: Indicates that image files are accepted.
A valid MIME type with no parameters: Indicates that files of the specified type are accepted.

The tokens must not be ASCII case-insensitive matches for any of the other tokens (i.e. duplicates are not allowed). To obtain the list of tokens from the attribute, the user agent must split the attribute value on commas.

User agents should prevent the user from selecting files that are not accepted by one (or more) of these tokens.

For historical reasons, the value IDL attribute prefixes the filename with the string "C:\fakepath\". Some legacy user agents actually included the full path (which was a security vulnerability). As a result of this, obtaining the filename from the value IDL attribute in a backwards-compatible way is non-trivial. The following function extracts the filename in a suitably compatible manner:

function extractFilename(path) {
  var x;
  x = path.lastIndexOf('\\');
  if (x >= 0) // Windows-based path
    return path.substr(x+1);
  x = path.lastIndexOf('/');
  if (x >= 0) // Unix-based path
    return path.substr(x+1);
  return path; // just the filename
}

This can be used as follows:

<p><input type=file name=image onchange="updateFilename(this.value)"></p>
<p>The name of the file you picked is: <span id="filename">(none)</span></p>
<script>
 function updateFilename(path) {
   var name = extractFilename(path);
   document.getElementById('filename').textContent = name;
 }
</script>

The following common input element content attributes apply to the element:

The following common input element content attributes and IDL attributes apply to the element: accept, multiple, and required; files and value IDL attributes.

The value IDL attribute is in mode filename.

The change event applies.

The following content attributes must not be specified and do not apply to the element: alt, autocomplete, checked, formaction, formenctype, formmethod, formnovalidate, formtarget, height, list, max, maxlength, min, pattern, placeholder, readonly, size, src, step, and width.

The element's value attribute must be omitted.

The following IDL attributes and methods do not apply to the element: checked, list, selectedOption, selectionStart, selectionEnd, valueAsDate, and valueAsNumber IDL attributes; select(), setSelectionRange(), stepDown(), and stepUp() methods.

The input event does not apply.

4.10.7.1.19 Submit Button state

Status: Last call for comments

When an input element's type attribute is in the Submit Button state, the rules in this section apply.

The input element represents a button that, when activated, submits the form. If the element has a value attribute, the button's label must be the value of that attribute; otherwise, it must be an implementation-defined string that means "Submit" or some such. The element is a button, specifically a submit button.

If the element is mutable, the user agent should allow the user to activate the element.

The element's activation behavior, if the element has a form owner, is to submit the form owner from the input element; otherwise, it is to do nothing.

The formaction, formenctype, formmethod, formnovalidate, and formtarget attributes are attributes for form submission.

The formnovalidate attribute can be used to make submit buttons that do not trigger the constraint validation.

The following common input element content attributes and IDL attributes apply to the element: formaction, formenctype, formmethod, formnovalidate, and formtarget content attributes; value IDL attribute.

The value IDL attribute is in mode default.

The following content attributes must not be specified and do not apply to the element: accept, alt, autocomplete, checked, height, list, max, maxlength, min, multiple, pattern, placeholder, readonly, required, size, src, step, and width.

The input and change events do not apply.

4.10.7.1.20 Image Button state

Status: Last call for comments

When an input element's type attribute is in the Image Button state, the rules in this section apply.

The input element represents either an image from which a user can select a coordinate and submit the form, or alternatively a button from which the user can submit the form. The element is a button, specifically a submit button.

The image is given by the src attribute. The src attribute must be present, and must contain a valid URL referencing a non-interactive, optionally animated, image resource that is neither paged nor scripted.

When any of the following events occur, unless the user agent cannot support images, or its support for images has been disabled, or the user agent only fetches elements on demand, the user agent must resolve the value of the src attribute, relative to the element, and if that is successful, must fetch the resulting absolute URL:

The input element's type attribute is first set to the Image Button state (possibly when the element is first created), and the src attribute is present.
The input element's type attribute is changed back to the Image Button state, and the src attribute is present, and its value has changed since the last time the type attribute was in the Image Button state.
The input element's type attribute is in the Image Button state, and the src attribute is set or changed.

Fetching the image must delay the load event of the element's document until the task that is queued by the networking task source once the resource has been fetched (defined below) has been run.

If the image was successfully obtained, with no network errors, and the image's type is a supported image type, and the image is a valid image of that type, then the image is said to be available. If this is true before the image is completely downloaded, each task that is queued by the networking task source while the image is being fetched must update the presentation of the image appropriately.

User agents must not support non-image resources with the input element. User agents must not run executable code embedded in the image resource. User agents must only display the first page of a multipage resource. User agents must not allow the resource to act in an interactive fashion, but should honor any animation in the resource.

The task that is queued by the networking task source once the resource has been fetched, must, if the download was successful and the image is available, queue a task to fire a simple event named load at the input element; and otherwise, if the fetching process fails without a response from the remote server, or completes but the image is not a valid or supported image, queue a task to fire a simple event named error on the input element.

The alt attribute provides the textual label for the alternative button for users and user agents who cannot use the image. The alt attribute must also be present, and must contain a non-empty string.

The input element supports dimension attributes.

If the src attribute is set, and the image is available and the user agent is configured to display that image, then: The element represents a control for selecting a coordinate from the image specified by the src attribute; if the element is mutable, the user agent should allow the user to select this coordinate. The activation behavior in this case consists of taking the user's selected coordinate, and then, if the element has a form owner, submitting the input element's form owner from the input element. If the user activates the control without explicitly selecting a coordinate, then the coordinate (0,0) must be assumed.

Otherwise, the element represents a submit button whose label is given by the value of the alt attribute; if the element is mutable, the user agent should allow the user to activate the button. The activation behavior in this case consists of setting the selected coordinate to (0,0), and then, if the element has a form owner, submitting the input element's form owner from the input element.

The selected coordinate must consist of an x-component and a y-component. The coordinates represent the position relative to the edge of the image, with the coordinate space having the positive x direction to the right, and the positive y direction downwards.

The x-component must be a valid integer representing a number x in the range −(border_left+padding_left) ≤ x ≤ width+border_right+padding_right, where width is the rendered width of the image, border_left is the width of the border on the left of the image, padding_left is the width of the padding on the left of the image, border_right is the width of the border on the right of the image, and padding_right is the width of the padding on the right of the image, with all dimensions given in CSS pixels.

The y-component must be a valid integer representing a number y in the range −(border_top+padding_top) ≤ y ≤ height+border_bottom+padding_bottom, where height is the rendered height of the image, border_top is the width of the border above the image, padding_top is the width of the padding above the image, border_bottom is the width of the border below the image, and padding_bottom is the width of the padding below the image, with all dimensions given in CSS pixels.

Where a border or padding is missing, its width is zero CSS pixels.

The formaction, formenctype, formmethod, formnovalidate, and formtarget attributes are attributes for form submission.

The following common input element content attributes and IDL attributes apply to the element: alt, formaction, formenctype, formmethod, formnovalidate, formtarget, height, src, and width content attributes; value IDL attribute.

The value IDL attribute is in mode default.

The following content attributes must not be specified and do not apply to the element: accept, autocomplete, checked, list, max, maxlength, min, multiple, pattern, placeholder, readonly, required, size, and step.

The element's value attribute must be omitted.

The input and change events do not apply.

Many aspects of this state's behavior are similar to the behavior of the img element. Readers are encouraged to read that section, where many of the same requirements are described in more detail.

4.10.7.1.21 Reset Button state

Status: Last call for comments

When an input element's type attribute is in the Reset Button state, the rules in this section apply.

The input element represents a button that, when activated, resets the form. If the element has a value attribute, the button's label must be the value of that attribute; otherwise, it must be an implementation-defined string that means "Reset" or some such. The element is a button.

If the element is mutable, the user agent should allow the user to activate the element.

The element's activation behavior, if the element has a form owner, is to reset the form owner; otherwise, it is to do nothing.

Constraint validation: The element is barred from constraint validation.

The value IDL attribute applies to this element and is in mode default.

The input and change events do not apply.

4.10.7.1.22 Button state

Status: Last call for comments

When an input element's type attribute is in the Button state, the rules in this section apply.

The input element represents a button with no default behavior. If the element has a value attribute, the button's label must be the value of that attribute; otherwise, it must be the empty string. The element is a button.

If the element is mutable, the user agent should allow the user to activate the element. The element's activation behavior is to do nothing.

Constraint validation: The element is barred from constraint validation.

The value IDL attribute applies to this element and is in mode default.

The input and change events do not apply.

4.10.7.2 Common `input` element attributes

Status: Last call for comments

These attributes only apply to an input element if its type attribute is in a state whose definition declares that the attribute applies. When an attribute doesn't apply to an input element, user agents must ignore the attribute, regardless of the requirements and definitions below.

4.10.7.2.1 The `autocomplete` attribute

Status: Last call for comments

User agents sometimes have features for helping users fill forms in, for example prefilling the user's address based on earlier user input.

The autocomplete attribute is an enumerated attribute. The attribute has three states. The on keyword maps to the on state, and the off keyword maps to the off state. The attribute may also be omitted. The missing value default is the default state.

The off state indicates either that the control's input data is particularly sensitive (for example the activation code for a nuclear weapon); or that it is a value that will never be reused (for example a one-time-key for a bank login) and the user will therefore have to explicitly enter the data each time, instead of being able to rely on the UA to prefill the value for him; or that the document provides its own autocomplete mechanism and does not want the user agent to provide autocompletion values.

Conversely, the on state indicates that the value is not particularly sensitive and the user can expect to be able to rely on his user agent to remember values he has entered for that control.

The default state indicates that the user agent is to use the autocomplete attribute on the element's form owner instead. (By default, the autocomplete attribute of form elements is in the on state.)

Each input element has a resulting autocompletion state, which is either on or off.

When an input element is in one of the following conditions, the input element's resulting autocompletion state is on; otherwise, the input element's resulting autocompletion state is off:

Its autocomplete attribute is in the on state.
Its autocomplete attribute is in the default state, and the element has no form owner.
Its autocomplete attribute is in the default state, and the element's form owner's autocomplete attribute is in the on state.

When an input element's resulting autocompletion state is on, the user agent may store the value entered by the user so that if the user returns to the page, the UA can prefill the form. Otherwise, the user agent should not remember the control's value, and should not offer past values to the user.

In addition, if the resulting autocompletion state is off, values are reset when traversing the history.

The autocompletion mechanism must be implemented by the user agent acting as if the user had modified the element's value, and must be done at a time where the element is mutable (e.g. just after the element has been inserted into the document, or when the user agent stops parsing).

Banks frequently do not want UAs to prefill login information:

<p><label>Account: <input type="text" name="ac" autocomplete="off"></label></p>
<p><label>PIN: <input type="password" name="pin" autocomplete="off"></label></p>

A user agent may allow the user to override the resulting autocompletion state and set it to always on, always allowing values to be remembered and prefilled), or always off, never remembering values. However, the ability to override the resulting autocompletion state to on should not be trivially accessible, as there are significant security implications for the user if all values are always remembered, regardless of the site's preferences.

4.10.7.2.2 The `list` attribute

Status: Last call for comments

The list attribute is used to identify an element that lists predefined options suggested to the user.

If present, its value must be the ID of a datalist element in the same document.

The suggestions source element is the first element in the document in tree order to have an ID equal to the value of the list attribute, if that element is a datalist element. If there is no list attribute, or if there is no element with that ID, or if the first element with that ID is not a datalist element, then there is no suggestions source element.

If there is a suggestions source element, then, when the user agent is allowing the user to edit the input element's value, the user agent should offer the suggestions represented by the suggestions source element to the user in a manner suitable for the type of control used. The user agent may use the suggestion's label to identify the suggestion if appropriate. If the user selects a suggestion, then the input element's value must be set to the selected suggestion's value, as if the user had written that value himself.

User agents must filter the suggestions to hide suggestions that the user would not be allowed to enter as the input element's value, and should filter the suggestions to hide suggestions that would cause the element to not satisfy its constraints.

If the list attribute does not apply, there is no suggestions source element.

This URL field offers some suggestions.

<label>Homepage: <input name=hp type=url list=hpurls></label>
<datalist id=hpurls>
 <option value="http://www.google.com/" label="Google">
 <option value="http://www.reddit.com/" label="Reddit">
</datalist>

Other URLs from the user's history might show also; this is up to the user agent.

This example demonstrates how to design a form that uses the autocompletion list feature while still degrading usefully in legacy user agents.

If the autocompletion list is merely an aid, and is not important to the content, then simply using a datalist element with children option elements is enough. To prevent the values from being rendered in legacy user agents, they should be placed inside the value attribute instead of inline.

<p>
 <label>
  Enter a breed:
  <input type="text" name="breed" list="breeds">
  <datalist id="breeds">
   <option value="Abyssinian">
   <option value="Alpaca">
   <!-- ... -->
  </datalist>
 </label>
</p>

However, if the values need to be shown in legacy UAs, then fallback content can be placed inside the datalist element, as follows:

<p>
 <label>
  Enter a breed:
  <input type="text" name="breed" list="breeds">
 </label>
 <datalist id="breeds">
  <label>
   or select one from the list:
   <select name="breed">
    <option value=""> (none selected)
    <option>Abyssinian
    <option>Alpaca
    <!-- ... -->
   </select>
  </label>
 </datalist>
</p>

The fallback content will only be shown in UAs that don't support datalist. The options, on the other hand, will be detected by all UAs, even though they are not direct children of the datalist element.

Note that if an option element used in a datalist is selected, it will be selected by default by legacy UAs (because it affects the select), but it will not have any effect on the input element in UAs that support datalist.

4.10.7.2.3 The `readonly` attribute

Status: Last call for comments

The readonly attribute is a boolean attribute that controls whether or not the use can edit the form control. When specified, the element is immutable.

Constraint validation: If the readonly attribute is specified on an input element, the element is barred from constraint validation.

In the following example, the existing product identifiers cannot be modified, but they are still displayed as part of the form, for consistency with the row representing a new product (where the identifier is not yet filled in).

<form action="products.cgi" method=post enctype="multipart/form-data">
 <table>
  <tr> <th> Product ID <th> Product name <th> Price <th> Action
  <tr>
   <td> <input readonly name="1.pid" value="H412">
   <td> <input required name="1.pname" value="Floor lamp Ulke">
   <td> $<input required type=number min=0 step=0.01 name="1.pprice" value="49.99">
   <td> <button formnovalidate name="action" value="delete:1">Delete</button>
  <tr>
   <td> <input readonly name="2.pid" value="FG28">
   <td> <input required name="2.pname" value="Table lamp Ulke">
   <td> $<input required type=number min=0 step=0.01 name="2.pprice" value="24.99">
   <td> <button formnovalidate name="action" value="delete:2">Delete</button>
  <tr>
   <td> <input required name="3.pid" value="" pattern="[A-Z0-9]+">
   <td> <input required name="3.pname" value="">
   <td> $<input required type=number min=0 step=0.01 name="3.pprice" value="">
   <td> <button formnovalidate name="action" value="delete:3">Delete</button>
 </table>
 <p> <button formnovalidate name="action" value="add">Add</button> </p>
 <p> <button name="action" value="update">Save</button> </p>
</form>

4.10.7.2.4 The `size` attribute

Status: Last call for comments

The size attribute gives the number of characters that, in a visual rendering, the user agent is to allow the user to see while editing the element's value.

The size attribute, if specified, must have a value that is a valid non-negative integer greater than zero.

If the attribute is present, then its value must be parsed using the rules for parsing non-negative integers, and if the result is a number greater than zero, then the user agent should ensure that at least that many characters are visible.

The size IDL attribute is limited to only non-negative numbers greater than zero.

4.10.7.2.5 The `required` attribute

Status: Last call for comments

The required attribute is a boolean attribute. When specified, the element is required.

Constraint validation: If the element is required, and its value IDL attribute applies and is in the mode value, and the element is mutable, and the element's value is the empty string, then the element is suffering from being missing.

The following form has two required fields, one for an e-mail address and one for a password. It also has a third field that is only considerd valid if the user types the same password in the password field and this third field.

<h1>Create new account</h1>
<form action="/newaccount" method=post>
 <p>
  <label for="username">E-mail address:</label>
  <input id="username" type=email required name=un>
 <p>
  <label for="password1">Password:</label>
  <input id="password1" type=password required name=up>
 <p>
  <label for="password2">Confirm password:</label>
  <input id="password2" type=password onforminput="setCustomValidity(value != password1.value ? 'Passwords do not match.' : '')">
 <p>
  <input type=submit value="Create account">
</form>

4.10.7.2.6 The `multiple` attribute

Status: Last call for comments

The multiple attribute is a boolean attribute that indicates whether the user is to be allowed to specify more than one value.

The following extract shows how an e-mail client's "Cc" field could accept multiple e-mail addresses.

<label>Cc: <input type=email multiple name=cc></label>

If the user had, amongst many friends in his user contacts database, two friends "Arthur Dent" (with address "art@example.net") and "Adam Josh" (with address "adamjosh@example.net"), then, after the user has typed "a", the user agent might suggest these two e-mail addresses to the user.

The page could also link in the user's contacts database from the site:

<label>Cc: <input type=email multiple name=cc list=contacts></label>
...
<datalist id="contacts">
 <option value="hedral@damowmow.com">
 <option value="pillar@example.com">
 <option value="astrophy@cute.example">
 <option value="astronomy@science.example.org">
</datalist>

Suppose the user had entered "bob@example.net" into this text field, and then started typing a second e-mail address starting with "a". The user agent might show both the two friends mentioned earlier, as well as the "astrophy" and "astronomy" values given in the datalist element.

The following extract shows how an e-mail client's "Attachments" field could accept multiple files for upload.

<label>Attachments: <input type=file multiple name=att></label>

4.10.7.2.7 The `maxlength` attribute

Status: Last call for comments

The maxlength attribute, when it applies, is a form control maxlength attribute controlled by the input element's dirty value flag.

If the input element has a maximum allowed value length, then the code-point length of the value of the element's value attribute must be equal to or less than the element's maximum allowed value length.

The following extract shows how a messaging client's text entry could be arbitrarily restricted to a fixed number of characters, thus forcing any conversion through this medium to be terse and discouraging intelligent discourse.

What are you doing? <input name=status maxlength=140>

4.10.7.2.8 The `pattern` attribute

Status: Last call for comments

The pattern attribute specifies a regular expression against which the control's value is to be checked.

If specified, the attribute's value must match the JavaScript Pattern production. [ECMA262]

Constraint validation: If the element's value is not the empty string, and the element's pattern attribute is specified and the attribute's value, when compiled as a JavaScript regular expression with the global, ignoreCase, and multiline flags disabled (see ECMA262 Edition 5, sections 15.10.7.2 through 15.10.7.4), compiles successfully but the resulting regular expression does not match the entirety of the element's value, then the element is suffering from a pattern mismatch. [ECMA262]

This implies that the regular expression language used for this attribute is the same as that used in JavaScript, except that the pattern attribute must match the entire value, not just any subset (somewhat as if it implied a ^(?: at the start of the pattern and a )$ at the end).

When an input element has a pattern attribute specified, authors should include a title attribute to give a description of the pattern. User agents may use the contents of this attribute, if it is present, when informing the user that the pattern is not matched, or at any other suitable time, such as in a tooltip or read out by assistive technology when the control gains focus.

For example, the following snippet:

<label> Part number:
 <input pattern="[0-9][A-Z]{3}" name="part"
        title="A part number is a digit followed by three uppercase letters."/>
</label>

...could cause the UA to display an alert such as:

A part number is a digit followed by three uppercase letters.
You cannot complete this form until the field is correct.

When a control has a pattern attribute, the title attribute, if used, must describe the pattern. Additional information could also be included, so long as it assists the user in filling in the control. Otherwise, assistive technology would be impaired.

For instance, if the title attribute contained the caption of the control, assistive technology could end up saying something like The text you have entered does not match the required pattern. Birthday, which is not useful.

UAs may still show the title in non-error situations (for example, as a tooltip when hovering over the control), so authors should be careful not to word titles as if an error has necessarily occurred.

4.10.7.2.9 The `min` and `max` attributes

Status: Last call for comments

The min and max attributes indicate the allowed range of values for the element.

Their syntax is defined by the section that defines the type attribute's current state.

If the element has a min attribute, and the result of applying the algorithm to convert a string to a number to the value of the min attribute is a number, then that number is the element's minimum; otherwise, if the type attribute's current state defines a default minimum, then that is the minimum; otherwise, the element has no minimum.

Constraint validation: When the element has a minimum, and the result of applying the algorithm to convert a string to a number to the string given by the element's value is a number, and the number obtained from that algorithm is less than the minimum, the element is suffering from an underflow.

The min attribute also defines the step base.

If the element has a max attribute, and the result of applying the algorithm to convert a string to a number to the value of the max attribute is a number, then that number is the element's maximum; otherwise, if the type attribute's current state defines a default maximum, then that is the maximum; otherwise, the element has no maximum.

Constraint validation: When the element has a maximum, and the result of applying the algorithm to convert a string to a number to the string given by the element's value is a number, and the number obtained from that algorithm is more than the maximum, the element is suffering from an overflow.

The max attribute's value (the maximum) must not be less than the min attribute's value (its minimum).

If an element has a maximum that is less than its minimum, then so long as the element has a value, it will either be suffering from an underflow or suffering from an overflow.

The following date control limits input to dates that are before the 1980s:

<input name=bday type=date max="1979-12-31">

The following number control limits input to whole numbers greater than zero:

<input name=quantity required type=number min=1 value=1>

4.10.7.2.10 The `step` attribute

Status: Last call for comments

The step attribute indicates the granularity that is expected (and required) of the value, by limiting the allowed values. The section that defines the type attribute's current state also defines the default step and the step scale factor, which are used in processing the attribute as described below.

The step attribute, if specified, must either have a value that is a valid floating point number that parses to a number that is greater than zero, or must have a value that is an ASCII case-insensitive match for the string "any".

The attribute provides the allowed value step for the element, as follows:

If the attribute is absent, then the allowed value step is the default step multiplied by the step scale factor.
Otherwise, if the attribute's value is an ASCII case-insensitive match for the string "any", then there is no allowed value step.
Otherwise, if the rules for parsing floating point number values, when they are applied to the attribute's value, return an error, zero, or a number less than zero, then the allowed value step is the default step multiplied by the step scale factor.
Otherwise, the allowed value step is the number returned by the rules for parsing floating point number values when they are applied to the attribute's value, multiplied by the step scale factor.

The step base is the result of applying the algorithm to convert a string to a number to the value of the min attribute, unless the element does not have a min attribute specified or the result of applying that algorithm is an error, in which case the step base is zero.

Constraint validation: When the element has an allowed value step, and the result of applying the algorithm to convert a string to a number to the string given by the element's value is a number, and that number subtracted from the step base is not an integral multiple of the allowed value step, the element is suffering from a step mismatch.

The following range control only accepts values in the range 0..1, and allows 256 steps in that range:

<input name=opacity type=range min=0 max=1 step=0.00392156863>

The following control allows any time in the day to be selected, with any accuracy (e.g. thousandth-of-a-second accuracy or more):

<input name=favtime type=time step=any>

Normally, time controls are limited to an accuracy of one minute.

4.10.7.2.11 The `placeholder` attribute

Status: Last call for comments

The placeholder attribute represents a short hint (a word or short phrase) intended to aid the user with data entry. A hint could be a sample value or a brief description of the expected format. The attribute, if specified, must have a value that contains no U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters.

For a longer hint or other advisory text, the title attribute is more appropriate.

The placeholder attribute should not be used as an alternative to a label.

User agents should present this hint to the user, after having stripped line breaks from it, when the element's value is the empty string and the control is not focused (e.g. by displaying it inside a blank unfocused control).

Here is an example of a mail configuration user interface that uses the placeholder attribute:

<fieldset>
 <legend>Mail Account</legend>
 <p><label>Name: <input type="text" name="fullname" placeholder="John Ratzenberger"></label></p>
 <p><label>Address: <input type="email" name="address" placeholder="john@example.net"></label></p>
 <p><label>Password: <input type="password" name="password"></label></p>
 <p><label>Description: <input type="text" name="desc" placeholder="My Email Account"></label></p>
</fieldset>

4.10.7.3 Common `input` element APIs

Status: Last call for comments

input . value [ = value ]

Returns the current value of the form control.

Can be set, to change the value.

Throws an INVALID_STATE_ERR exception if it is set to any value other than the empty string when the control is a file upload control.

input . checked [ = value ]

Returns the current checkedness of the form control.

Can be set, to change the checkedness.

input . files

Returns a FileList object listing the selected files of the form control.

Throws an INVALID_STATE_ERR exception if the control isn't a file control.

input . valueAsDate [ = value ]

Returns a Date object representing the form control's value, if applicable; otherwise, returns null.

Can be set, to change the value.

Throws an INVALID_STATE_ERR exception if the control isn't date- or time-based.

input . valueAsNumber [ = value ]

Returns a number representing the form control's value, if applicable; otherwise, returns null.

Can be set, to change the value.

Throws an INVALID_STATE_ERR exception if the control is neither date- or time-based nor numeric.

input . stepUp( [ n ] )

input . stepDown( [ n ] )

Changes the form control's value by the value given in the step attribute, multiplied by n. The default is 1.

Throws INVALID_STATE_ERR exception if the control is neither date- or time-based nor numeric, if the step attribute's value is "any", if the current value could not be parsed, or if stepping in the given direction by the given amount would take the value out of range.

input . list

Returns the datalist element indicated by the list attribute.

input . selectedOption

Returns the option element from the datalist element indicated by the list attribute that matches the form control's value.

The value IDL attribute allows scripts to manipulate the value of an input element. The attribute is in one of the following modes, which define its behavior:

value: On getting, it must return the current value of the element. On setting, it must set the element's value to the new value, set the element's dirty value flag to true, and then invoke the value sanitization algorithm, if the element's type attribute's current state defines one.
default: On getting, if the element has a value attribute, it must return that attribute's value; otherwise, it must return the empty string. On setting, it must set the element's value attribute to the new value.
default/on: On getting, if the element has a value attribute, it must return that attribute's value; otherwise, it must return the string "on". On setting, it must set the element's value attribute to the new value.
filename: On getting, it must return the string "C:\fakepath\" followed by the filename of the first file in the list of selected files, if any, or the empty string if the list is empty. On setting, if the new value is the empty string, it must empty the list of selected files; otherwise, it must throw an INVALID_STATE_ERR exception.

The checked IDL attribute allows scripts to manipulate the checkedness of an input element. On getting, it must return the current checkedness of the element; and on setting, it must set the element's checkedness to the new value and set the element's dirty checkedness flag to true.

The files IDL attribute allows scripts to access the element's selected files. On getting, if the IDL attribute applies, it must return a FileList object that represents the current selected files. The same object must be returned until the list of selected files changes. If the IDL attribute does not apply, then it must instead throw an INVALID_STATE_ERR exception. [FILEAPI]

The valueAsDate IDL attribute represents the value of the element, interpreted as a date.

On getting, if the valueAsDate attribute does not apply, as defined for the input element's type attribute's current state, then return null. Otherwise, run the algorithm to convert a string to a Date object defined for that state; if the algorithm returned a Date object, then return it, otherwise, return null.

On setting, if the valueAsDate attribute does not apply, as defined for the input element's type attribute's current state, then throw an INVALID_STATE_ERR exception; otherwise, if the new value is null, then set the value of the element to the empty string; otherwise, run the algorithm to convert a Date object to a string, as defined for that state, on the new value, and set the value of the element to resulting string.

The valueAsNumber IDL attribute represents the value of the element, interpreted as a number.

On getting, if the valueAsNumber attribute does not apply, as defined for the input element's type attribute's current state, then return a Not-a-Number (NaN) value. Otherwise, if the valueAsDate attribute applies, run the algorithm to convert a string to a Date object defined for that state; if the algorithm returned a Date object, then return the time value of the object (the number of milliseconds from midnight UTC the morning of 1970-01-01 to the time represented by the Date object), otherwise, return a Not-a-Number (NaN) value. Otherwise, run the algorithm to convert a string to a number defined for that state; if the algorithm returned a number, then return it, otherwise, return a Not-a-Number (NaN) value.

On setting, if the valueAsNumber attribute does not apply, as defined for the input element's type attribute's current state, then throw an INVALID_STATE_ERR exception. Otherwise, if the valueAsDate attribute applies, run the algorithm to convert a Date object to a string defined for that state, passing it a Date object whose time value is the new value, and set the value of the element to resulting string. Otherwise, run the algorithm to convert a number to a string, as defined for that state, on the new value, and set the value of the element to resulting string.

The stepDown(n) and stepUp(n) methods, when invoked, must run the following algorithm:

If the stepDown() and stepUp() methods do not apply, as defined for the input element's type attribute's current state, then throw an INVALID_STATE_ERR exception, and abort these steps.
If the element has no allowed value step, then throw an INVALID_STATE_ERR exception, and abort these steps.
If applying the algorithm to convert a string to a number to the string given by the element's value results in an error, then throw an INVALID_STATE_ERR exception, and abort these steps; otherwise, let value be the result of that algorithm.
Let n be the argument, or 1 if the argument was omitted.
Let delta be the allowed value step multiplied by n.
If the method invoked was the stepDown() method, negate delta.
Let value be the result of adding delta to value.
If the element has a minimum, and the value is less than that minimum, then throw a INVALID_STATE_ERR exception.
If the element has a maximum, and the value is greater than that maximum, then throw a INVALID_STATE_ERR exception.
Let value as string be the result of running the algorithm to convert a number to a string, as defined for the input element's type attribute's current state, on value.
Set the value of the element to value as string.

The list IDL attribute must return the current suggestions source element, if any, or null otherwise.

The selectedOption IDL attribute must return the first option element, in tree order, to be a child of the suggestions source element and whose value matches the input element's value, if any. If there is no suggestions source element, or if it contains no matching option element, then the selectedOption attribute must return null.

4.10.7.4 Common event behaviors

Status: Last call for comments

When the input event applies, any time the user causes the element's value to change, the user agent must queue a task to fire a simple event that bubbles named input at the input element, then broadcast forminput events at the input element's form owner. User agents may wait for a suitable break in the user's interaction before queuing the task; for example, a user agent could wait for the user to have not hit a key for 100ms, so as to only fire the event when the user pauses, instead of continuously for each keystroke.

Examples of a user changing the element's value would include the user typing into a text field, pasting a new value into the field, or undoing an edit in that field. Some user interactions do not cause changes to the value, e.g. hitting the "delete" key in an empty text field, or replacing some text in the field with text from the clipboard that happens to be exactly the same text.

When the change event applies, if the element does not have an activation behavior defined but uses a user interface that involves an explicit commit action, then any time the user commits a change to the element's value or list of selected files, the user agent must queue a task to fire a simple event that bubbles named change at the input element, then broadcast formchange events at the input element's form owner.

An example of a user interface with a commit action would be a File Upload control that consists of a single button that brings up a file selection dialog: when the dialog is closed, if that the file selection changed as a result, then the user has committed a new file selection.

Another example of a user interface with a commit action would be a Date control that allows both text-based user input and user selection from a drop-down calendar: while text input might not have an explicit commit step, selecting a date from the drop down calendar and then dismissing the drop down would be a commit action.

When the user agent changes the element's value on behalf of the user (e.g. as part of a form prefilling feature), the user agent must follow these steps:

If the input event applies, queue a task to fire a simple event that bubbles named input at the input element.
If the input event applies, broadcast forminput events at the input element's form owner.
If the change event applies, queue a task to fire a simple event that bubbles named change at the input element.
If the change event applies, broadcast formchange events at the input element's form owner.

In addition, when the change event applies, change events can also be fired as part of the element's activation behavior and as part of the unfocusing steps.

The task source for these tasks is the user interaction task source.

4.10.8 The `button` element

Status: Last call for comments

Categories

Listed, labelable, and submittable form-associated element.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Phrasing content, but there must be no interactive content descendant.

Content attributes:

autofocus

disabled

form

formaction

formenctype

formmethod

formnovalidate

formtarget

name

type

value

DOM interface:

interface HTMLButtonElement : HTMLElement {
           attribute boolean autofocus;
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
           attribute DOMString formAction;
           attribute DOMString formEnctype;
           attribute DOMString formMethod;
           attribute DOMString formNoValidate;
           attribute DOMString formTarget;
           attribute DOMString name;
           attribute DOMString type;
           attribute DOMString value;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);

  readonly attribute NodeList labels;
};

The button element represents a button. If the element is not disabled, then the user agent should allow the user to activate the button.

The element is a button.

The type attribute controls the behavior of the button when it is activated. It is an enumerated attribute. The following table lists the keywords and states for the attribute — the keywords in the left column map to the states in the cell in the second column on the same row as the keyword.

Keyword	State	Brief description
`submit`	Submit Button	Submits the form.
`reset`	Reset Button	Resets the form.
`button`	Button	Does nothing.

The missing value default is the Submit Button state.

If the type attribute is in the Submit Button state, the element is specifically a submit button.

Constraint validation: If the type attribute is in the Reset Button state or the Button state, the element is barred from constraint validation.

If the element is not disabled, the activation behavior of the button element is to run the steps defined in the following list for the current state of the element's type attribute.

Submit Button: If the element has a form owner, the element must submit the form owner from the button element.
Reset Button: If the element has a form owner, the element must reset the form owner.
Button: Do nothing.

The form attribute is used to explicitly associate the button element with its form owner. The name attribute represents the element's name. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The autofocus attribute controls focus. The formaction, formenctype, formmethod, formnovalidate, and formtarget attributes are attributes for form submission.

The formnovalidate attribute can be used to make submit buttons that do not trigger the constraint validation.

The formaction, formenctype, formmethod, formnovalidate, and formtarget must not be specified if the element's type attribute is not in the Submit Button state.

The value attribute gives the element's value for the purposes of form submission. The element's value is the value of the element's value attribute, if there is one, or the empty string otherwise.

A button (and its value) is only included in the form submission if the button itself was used to initiate the form submission.

The value and type IDL attributes must reflect the respective content attributes of the same name.

The following button is labeled "Show hint" and pops up a dialog box when activated:

<button type=button
        onclick="alert('This 15-20 minute piece was composed by George Gershwin.')">
 Show hint
</button>

4.10.9 The `select` element

Status: Last call for comments

Categories

Listed, labelable, submittable, and resettable form-associated element.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Zero or more option or optgroup elements.

Content attributes:

autofocus

disabled

form

multiple

name

size

DOM interface:

interface HTMLSelectElement : HTMLElement {
           attribute boolean autofocus;
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
           attribute boolean multiple;
           attribute DOMString name;
           attribute unsigned long size;

  readonly attribute DOMString type;

  readonly attribute HTMLOptionsCollection options;
           attribute unsigned long length;
  caller getter any item(in unsigned long index);
  caller getter any namedItem(in DOMString name);
  void add(in HTMLElement element, in optional HTMLElement before);
  void add(in HTMLElement element, in long before);
  void remove(in long index);

  readonly attribute HTMLCollection selectedOptions;
           attribute long selectedIndex;
           attribute DOMString value;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);

  readonly attribute NodeList labels;
};

The select element represents a control for selecting amongst a set of options.

The multiple attribute is a boolean attribute. If the attribute is present, then the select element represents a control for selecting zero or more options from the list of options. If the attribute is absent, then the select element represents a control for selecting a single option from the list of options.

The list of options for a select element consists of all the option element children of the select element, and all the option element children of all the optgroup element children of the select element, in tree order.

The size attribute gives the number of options to show to the user. The size attribute, if specified, must have a value that is a valid non-negative integer greater than zero. If the multiple attribute is present, then the size attribute's default value is 4. If the multiple attribute is absent, then the size attribute's default value is 1.

If the multiple attribute is absent, and the element is not disabled, then the user agent should allow the user to pick an option element in its list of options that is itself not disabled. Upon this option element being picked (either through a click, or through unfocusing the element after changing its value, or through a menu command, or through any other mechanism), and before the relevant user interaction event is queued (e.g. before the click event), the user agent must set the selectedness of the picked option element to true and then queue a task to fire a simple event that bubbles named change at the select element, using the user interaction task source as the task source, then broadcast formchange events at the element's form owner.

If the multiple attribute is absent, whenever an option element in the select element's list of options has its selectedness set to true, and whenever an option element with its selectedness set to true is added to the select element's list of options, the user agent must set the selectedness of all the other option element in its list of options to false.

If the multiple attribute is absent, whenever there are no option elements in the select element's list of options that have their selectedness set to true, the user agent must set the selectedness of the first option element in the list of options in tree order that is not disabled, if any, to true.

If the multiple attribute is present, and the element is not disabled, then the user agent should allow the user to toggle the selectedness of the option elements in its list of options that are themselves not disabled (either through a click, or through a menu command, or any other mechanism). Upon the selectedness of one or more option elements being changed by the user, and before the relevant user interaction event is queued (e.g. before a related click event), the user agent must queue a task to fire a simple event that bubbles named change at the select element, using the user interaction task source as the task source, then broadcast formchange events at the element's form owner.

The reset algorithm for select elements is to go through all the option elements in the element's list of options, and set their selectedness to true if the option element has a selected attribute, and false otherwise.

The form attribute is used to explicitly associate the select element with its form owner. The name attribute represents the element's name. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The autofocus attribute controls focus.

select . type

Returns "select-multiple" if the element has a multiple attribute, and "select-one" otherwise.

select . options

Returns an HTMLOptionsCollection of the list of options.

select . length [ = value ]

Returns the number of elements in the list of options.

When set to a smaller number, truncates the number of option elements in the select.

When set to a greater number, adds new blank option elements to the select.

element = select . item(index)

select[index]

select(index)

Returns the item with index index from the list of options. The items are sorted in tree order.

Returns null if index is out of range.

element = select . namedItem(name)

select[name]

select(name)

Returns the item with ID or name name from the list of options.

If there are multiple matching items, then a NodeList object containing all those elements is returned.

Returns null if no element with that ID could be found.

select . add(element [, before ])

Inserts element before the node given by before.

The before argument can be a number, in which case element is inserted before the item with that number, or an element from the list of options, in which case element is inserted before that element.

If before is omitted, null, or a number out of range, then element will be added at the end of the list.

select . selectedOptions

Returns an HTMLCollection of the list of options that are selected.

select . selectedIndex [ = value ]

Returns the index of the first selected item, if any, or −1 if there is no selected item.

Can be set, to change the selection.

select . value [ = value ]

Returns the value of the first selected item, if any, or the empty string if there is no selected item.

Can be set, to change the selection.

The type IDL attribute, on getting, must return the string "select-one" if the multiple attribute is absent, and the string "select-multiple" if the multiple attribute is present.

The options IDL attribute must return an HTMLOptionsCollection rooted at the select node, whose filter matches the elements in the list of options.

The options collection is also mirrored on the HTMLSelectElement object. The indices of the supported indexed properties at any instant are the indices supported by the object returned by the options attribute at that instant. The names of the supported named properties at any instant are the names supported by the object returned by the options attribute at that instant.

The length IDL attribute must return the number of nodes represented by the options collection. On setting, it must act like the attribute of the same name on the options collection.

The item(index) method must return the value returned by the method of the same name on the options collection, when invoked with the same argument.

The namedItem(name) method must return the value returned by the method of the same name on the options collection, when invoked with the same argument.

Similarly, the add() and remove() methods must act like their namesake methods on that same options collection.

The selectedOptions IDL attribute must return an HTMLCollection rooted at the select node, whose filter matches the elements in the list of options that have their selectedness set to true.

The selectedIndex IDL attribute, on getting, must return the index of the first option element in the list of options in tree order that has its selectedness set to true, if any. If there isn't one, then it must return −1.

On setting, the selectedIndex attribute must set the selectedness of all the option elements in the list of options to false, and then the option element in the list of options whose index is the given new value, if any, must have its selectedness set to true.

The value IDL attribute, on getting, must return the value of the first option element in the list of options in tree order that has its selectedness set to true, if any. If there isn't one, then it must return the empty string.

On setting, the value attribute must set the selectedness of all the option elements in the list of options to false, and then first the option element in the list of options, in tree order, whose value is equal to the given new value, if any, must have its selectedness set to true.

The multiple and size IDL attributes must reflect the respective content attributes of the same name. The size IDL attribute limited to only non-negative numbers greater than zero.

The following example shows how a select element can be used to offer the user with a set of options from which the user can select a single option. The default option is preselected.

<p>
 <label for="unittype">Select unit type:</label>
 <select id="unittype" name="unittype">
  <option value="1"> Miner </option>
  <option value="2"> Puffer </option>
  <option value="3" selected> Snipey </option>
  <option value="4"> Max </option>
  <option value="5"> Firebot </option>
 </select>
</p>

Here, the user is offered a set of options from which he can select any number. By default, all five options are selected.

<p>
 <label for="allowedunits">Select unit types to enable on this map:</label>
 <select id="allowedunits" name="allowedunits" multiple>
  <option value="1" selected> Miner </option>
  <option value="2" selected> Puffer </option>
  <option value="3" selected> Snipey </option>
  <option value="4" selected> Max </option>
  <option value="5" selected> Firebot </option>
 </select>
</p>

4.10.10 The `datalist` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Either: phrasing content.

Or: Zero or more option elements.

Content attributes:

DOM interface:

interface HTMLDataListElement : HTMLElement {
  readonly attribute HTMLCollection options;
};

The datalist element represents a set of option elements that represent predefined options for other controls. The contents of the element represents fallback content for legacy user agents, intermixed with option elements that represent the predefined options. In the rendering, the datalist element represents nothing and it, along with its children, should be hidden.

The datalist element is hooked up to an input element using the list attribute on the input element.

Each option element that is a descendant of the datalist element, that is not disabled, and whose value is a string that isn't the empty string, represents a suggestion. Each suggestion has a value and a label.

datalist . options: Returns an HTMLCollection of the options elements of the table.

The options IDL attribute must return an HTMLCollection rooted at the datalist node, whose filter matches option elements.

Constraint validation: If an element has a datalist element ancestor, it is barred from constraint validation.

4.10.11 The `optgroup` element

Status: Last call for comments

Categories

None.

Contexts in which this element may be used:

As a child of a select element.

Content model:

Zero or more option elements.

Content attributes:

disabled

label

DOM interface:

interface HTMLOptGroupElement : HTMLElement {
           attribute boolean disabled;
           attribute DOMString label;
};

The optgroup element represents a group of option elements with a common label.

The element's group of option elements consists of the option elements that are children of the optgroup element.

When showing option elements in select elements, user agents should show the option elements of such groups as being related to each other and separate from other option elements.

The disabled attribute is a boolean attribute and can be used to disable a group of option elements together.

The label attribute must be specified. Its value gives the name of the group, for the purposes of the user interface. User agents should use this attribute's value when labelling the group of option elements in a select element.

The disabled and label attributes must reflect the respective content attributes of the same name.

The following snippet shows how a set of lessons from three courses could be offered in a select drop-down widget:

<form action="courseselector.dll" method="get">
 <p>Which course would you like to watch today?
 <p><label>Course:
  <select name="c">
   <optgroup label="8.01 Physics I: Classical Mechanics">
    <option value="8.01.1">Lecture 01: Powers of Ten
    <option value="8.01.2">Lecture 02: 1D Kinematics
    <option value="8.01.3">Lecture 03: Vectors
   <optgroup label="8.02 Electricity and Magnestism">
    <option value="8.02.1">Lecture 01: What holds our world together?
    <option value="8.02.2">Lecture 02: Electric Field
    <option value="8.02.3">Lecture 03: Electric Flux
   <optgroup label="8.03 Physics III: Vibrations and Waves">
    <option value="8.03.1">Lecture 01: Periodic Phenomenon
    <option value="8.03.2">Lecture 02: Beats
    <option value="8.03.3">Lecture 03: Forced Oscillations with Damping
  </select>
 </label>
 <p><input type=submit value="▶ Play">
</form>

4.10.12 The `option` element

Status: Last call for comments

Categories

None.

Contexts in which this element may be used:

As a child of a select element.

As a child of a datalist element.

As a child of an optgroup element.

Content model:

Text.

Content attributes:

disabled

label

selected

value

DOM interface:

[NamedConstructor=Option(),
 NamedConstructor=Option(in DOMString text),
 NamedConstructor=Option(in DOMString text, in DOMString value),
 NamedConstructor=Option(in DOMString text, in DOMString value, in boolean defaultSelected),
 NamedConstructor=Option(in DOMString text, in DOMString value, in boolean defaultSelected, in boolean selected)]
interface HTMLOptionElement : HTMLElement {
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
           attribute DOMString label;
           attribute boolean defaultSelected;
           attribute boolean selected;
           attribute DOMString value;

           attribute DOMString text;
  readonly attribute long index;
};

The option element represents an option in a select element or as part of a list of suggestions in a datalist element.

The disabled attribute is a boolean attribute. An option element is disabled if its disabled attribute is present or if it is a child of an optgroup element whose disabled attribute is present.

An option element that is disabled must prevent any click events that are queued on the user interaction task source from being dispatched on the element.

The label attribute provides a label for element. The label of an option element is the value of the label attribute, if there is one, or the textContent of the element, if there isn't.

The value attribute provides a value for element. The value of an option element is the value of the value attribute, if there is one, or the textContent of the element, if there isn't.

The selected attribute represents the default selectedness of the element.

The selectedness of an option element is a boolean state, initially false. If the element is disabled, then the element's selectedness is always false and cannot be set to true. Except where otherwise specified, when the element is created, its selectedness must be set to true if the element has a selected attribute. Whenever an option element's selected attribute is added, its selectedness must be set to true.

The Option() constructor with three or fewer arguments overrides the initial state of the selectedness state to always be false even if the third argument is true (implying that a selected attribute is to be set). The fourth argument can be used to explicitly set the initial selectedness state when using the constructor.

An option element's index is the number of option element that are in the same list of options but that come before it in tree order. If the option element is not in a list of options, then the option element's index is zero.

option . selected

Returns true if the element is selected, and false otherwise.

option . index

Returns the index of the element in its select element's options list.

option . form

Returns the element's form element, if any, or null otherwise.

option . text

Same as textContent.

option = new Option( [ text [, value [, defaultSelected [, selected ] ] ] ] )

Returns a new option element.

The text argument sets the contents of the element.

The value argument sets the value attribute.

The defaultSelected argument sets the selected attribute.

The selected argument sets whether or not the element is selected. If it is omitted, even if the defaultSelected argument is true, the element is not selected.

The disabled and label IDL attributes must reflect the respective content attributes of the same name. The defaultSelected IDL attribute must reflect the selected content attribute.

The value IDL attribute, on getting, must return the value of the element's value content attribute, if it has one, or else the value of the element's textContent IDL attribute. On setting, the element's value content attribute must be set to the new value.

The selected IDL attribute must return true if the element's selectedness is true, and false otherwise.

The index IDL attribute must return the element's index.

The form IDL attribute's behavior depends on whether the option element is in a select element or not. If the option has a select element as its parent, or has a colgroup element as its parent and that colgroup element has a select element as its parent, then the form IDL attribute must return the same value as the form IDL attribute on that select element. Otherwise, it must return null.

Several constructors are provided for creating HTMLOptionElement objects (in addition to the factory methods from DOM Core such as createElement()): Option(), Option(text), Option(text, value), Option(text, value, defaultSelected), and Option(text, value, defaultSelected, selected). When invoked as constructors, these must return a new HTMLOptionElement object (a new option element). If the text argument is present, the new object must have as its only child a Node with node type TEXT_NODE (3) whose data is the value of that argument. If the value argument is present, the new object must have a value attribute set with the value of the argument as its value. If the defaultSelected argument is present and true, the new object must have a selected attribute set with no value. If the selected argument is present and true, the new object must have its selectedness set to true; otherwise the fourth argument is absent or false, and the selectedness must be set to false, even if the defaultSelected argument is present and true. The element's document must be the active document of the browsing context of the Window object on which the interface object of the invoked constructor is found.

4.10.13 The `textarea` element

Status: Last call for comments

Categories

Listed, labelable, submittable, and resettable form-associated element.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Text.

Content attributes:

autofocus

cols

disabled

form

maxlength

name

placeholder

readonly

required

rows

wrap

DOM interface:

interface HTMLTextAreaElement : HTMLElement {
           attribute boolean autofocus;
           attribute unsigned long cols;
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
           attribute long maxLength;
           attribute DOMString name;
           attribute DOMString placeholder;
           attribute boolean readOnly;
           attribute boolean required;
           attribute unsigned long rows;
           attribute DOMString wrap;

  readonly attribute DOMString type;
           attribute DOMString defaultValue;
           attribute DOMString value;
  readonly attribute unsigned long textLength;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);

  readonly attribute NodeList labels;

  void select();
           attribute unsigned long selectionStart;
           attribute unsigned long selectionEnd;
  void setSelectionRange(in unsigned long start, in unsigned long end);
};

The textarea element represents a multiline plain text edit control for the element's raw value. The contents of the control represent the control's default value.

The raw value of a textarea control must be initially the empty string.

The readonly attribute is a boolean attribute used to control whether the text can be edited by the user or not.

Constraint validation: If the readonly attribute is specified on a textarea element, the element is barred from constraint validation.

A textarea element is mutable if it is neither disabled nor has a readonly attribute specified.

When a textarea is mutable, its raw value should be editable by the user. Any time the user causes the element's raw value to change, the user agent must queue a task to fire a simple event that bubbles named input at the textarea element, then broadcast forminput events at the textarea element's form owner. User agents may wait for a suitable break in the user's interaction before queuing the task; for example, a user agent could wait for the user to have not hit a key for 100ms, so as to only fire the event when the user pauses, instead of continuously for each keystroke.

A textarea element has a dirty value flag, which must be initially set to false, and must be set to true whenever the user interacts with the control in a way that changes the raw value.

When the textarea element's textContent IDL attribute changes value, if the element's dirty value flag is false, then the element's raw value must be set to the value of the element's textContent IDL attribute.

The reset algorithm for textarea elements is to set the element's value to the value of the element's textContent IDL attribute.

The cols attribute specifies the expected maximum number of characters per line. If the cols attribute is specified, its value must be a valid non-negative integer greater than zero. If applying the rules for parsing non-negative integers to the attribute's value results in a number greater than zero, then the element's character width is that value; otherwise, it is 20.

The user agent may use the textarea element's character width as a hint to the user as to how many characters the server prefers per line (e.g. for visual user agents by making the width of the control be that many characters). In visual renderings, the user agent should wrap the user's input in the rendering so that each line is no wider than this number of characters.

The rows attribute specifies the number of lines to show. If the rows attribute is specified, its value must be a valid non-negative integer greater than zero. If applying the rules for parsing non-negative integers to the attribute's value results in a number greater than zero, then the element's character height is that value; otherwise, it is 2.

Visual user agents should set the height of the control to the number of lines given by character height.

The wrap attribute is an enumerated attribute with two keywords and states: the soft keyword which maps to the Soft state, and the hard keyword which maps to the Hard state. The missing value default is the Soft state.

If the element's wrap attribute is in the Hard state, the cols attribute must be specified.

The element's value is defined to be the element's raw value with the following transformation applied:

Replace every occurrence of a U+000D CARRIAGE RETURN (CR) character not followed by a U+000A LINE FEED (LF) character, and every occurrence of a U+000A LINE FEED (LF) character not preceded by a U+000D CARRIAGE RETURN (CR) character, by a two-character string consisting of a U+000D CARRIAGE RETURN U+000A LINE FEED (CRLF) character pair.
If the element's wrap attribute is in the Hard state, insert U+000D CARRIAGE RETURN U+000A LINE FEED (CRLF) character pairs into the string using a UA-defined algorithm so that each line has no more than character width characters. For the purposes of this requirement, lines are delimited by the start of the string, the end of the string, and U+000D CARRIAGE RETURN U+000A LINE FEED (CRLF) character pairs.

The maxlength attribute is a form control maxlength attribute controlled by the textarea element's dirty value flag.

If the textarea element has a maximum allowed value length, then the element's children must be such that the code-point length of the value of the element's textContent IDL attribute is equal to or less than the element's maximum allowed value length.

The required attribute is a boolean attribute. When specified, the user will be required to enter a value before submitting the form.

Constraint validation: If the element has its required attribute specified, and the element is mutable, and the element's value is the empty string, then the element is suffering from being missing.

The placeholder attribute represents a hint (a word or short phrase) intended to aid the user with data entry. A hint could be a sample value or a brief description of the expected format. The attribute, if specified, must have a value that contains no U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters.

For a longer hint or other advisory text, the title attribute is more appropriate.

The placeholder attribute should not be used as an alternative to a label.

The form attribute is used to explicitly associate the textarea element with its form owner. The name attribute represents the element's name. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The autofocus attribute controls focus.

textarea . type

Returns the string "textarea".

textarea . value

Returns the current value of the element.

Can be set, to change the value.

The cols, placeholder, required, rows, and wrap attributes must reflect the respective content attributes of the same name. The cols and rows attributes are limited to only non-negative numbers greater than zero. The maxLength IDL attribute must reflect the maxlength content attribute, limited to only non-negative numbers. The readOnly IDL attribute must reflect the readonly content attribute.

The type IDL attribute must return the value "textarea".

The defaultValue IDL attribute must act like the element's textContent IDL attribute.

The value attribute must, on getting, return the element's raw value; on setting, it must set the element's raw value to the new value.

The textLength IDL attribute must return the code-point length of the element's value.

Here is an example of a textarea being used for unrestricted free-form text input in a form:

<p>If you have any comments, please let us know: <textarea cols=80 name=comments></textarea></p>

4.10.14 The `keygen` element

Status: Last call for comments

Categories

Listed, labelable, submittable, and resettable form-associated element.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Empty.

Content attributes:

autofocus

challenge

disabled

form

keytype

name

DOM interface:

interface HTMLKeygenElement : HTMLElement {
           attribute boolean autofocus;
           attribute DOMString challenge;
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
           attribute DOMString keytype;
           attribute DOMString name;

  readonly attribute DOMString type;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);

  readonly attribute NodeList labels;
};

The keygen element represents a key pair generator control. When the control's form is submitted, the private key is stored in the local keystore, and the public key is packaged and sent to the server.

The challenge attribute may be specified. Its value will be packaged with the submitted key.

The keytype attribute is an enumerated attribute. The following table lists the keywords and states for the attribute — the keywords in the left column map to the states listed in the cell in the second column on the same row as the keyword. User agents are not required to support these values, and must only recognise values whose corresponding algorithms they support.

Keyword	State
`rsa`	RSA

The invalid value default state is the unknown state. The missing value default state is the RSA state, if it is supported, or the unknown state otherwise.

This specification does not specify what key types user agents are to support — it is possible for a user agent to not support any key types at all.

The user agent may expose a user interface for each keygen element to allow the user to configure settings of the element's key pair generator, e.g. the key length.

The reset algorithm for keygen elements is to set these various configuration settings back to their defaults.

The element's value is the string returned from the following algorithm:

Use the appropriate step from the following list:

If the keytype attribute is in the RSA state

Generate an RSA key pair using the settings given by the user, if appropriate, using the md5WithRSAEncryption RSA signature algorithm (the signature algorithm with MD5 and the RSA encryption algorithm) referenced in section 2.2.1 ("RSA Signature Algorithm") of RFC 3279, and defined in RFC 2313. [RFC3279] [RFC2313]

Otherwise, the keytype attribute is in the unknown state

The given key type is not supported. Return the empty string and abort this algorithm.

Let private key be the generated private key.

Let public key be the generated public key.

Let signature algorithm be the selected signature algorithm.
If the element has a challenge attribute, then let challenge be that attribute's value. Otherwise, let challenge be the empty string.
Let algorithm be an ASN.1 AlgorithmIdentifier structure as defined by RFC 5280, with the algorithm field giving the ASN.1 OID used to identify signature algorithm, using the OIDs defined in section 2.2 ("Signature Algorithms") of RFC 3279, and the parameters field set up as required by RFC 3279 for AlgorithmIdentifier structures for that algorithm. [X690] [RFC5280] [RFC3279]
Let spki be an ASN.1 SubjectPublicKeyInfo structure as defined by RFC 5280, with the algorithm field set to the algorithm structure from the previous step, and the subjectPublicKey field set to the BIT STRING value resulting from ASN.1 DER encoding the public key. [X690] [RFC5280]
Let publicKeyAndChallenge be an ASN.1 PublicKeyAndChallenge structure as defined below, with the spki field set to the spki structure from the previous step, and the challenge field set to the string challenge obtained earlier. [X690]
Let signature be the BIT STRING value resulting from ASN.1 DER encoding the signature generated by applying the signature algorithm to the byte string obtained by ASN.1 DER encoding the publicKeyAndChallenge structure, using private key as the signing key. [X690]
Let signedPublicKeyAndChallenge be an ASN.1 SignedPublicKeyAndChallenge structure as defined below, with the publicKeyAndChallenge field set to the publicKeyAndChallenge structure, the signatureAlgorithm field set to the algorithm structure, and the signature field set to the BIT STRING signature from the previous step. [X690]
Return the result of base64 encoding the result of ASN.1 DER encoding the signedPublicKeyAndChallenge structure. [RFC3548] [X690]

The data objects used by the above algorithm are defined as follows. These definitions use the same "ASN.1-like" syntax defined by RFC 5280. [RFC5280]

PublicKeyAndChallenge ::= SEQUENCE {
    spki SubjectPublicKeyInfo,
    challenge IA5STRING
}

SignedPublicKeyAndChallenge ::= SEQUENCE {
    publicKeyAndChallenge PublicKeyAndChallenge,
    signatureAlgorithm AlgorithmIdentifier,
    signature BIT STRING
}

Constraint validation: The keygen element is barred from constraint validation.

The form attribute is used to explicitly associate the keygen element with its form owner. The name attribute represents the element's name. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The autofocus attribute controls focus.

keygen . type: Returns the string "keygen".

The challenge IDL attribute must reflect the content attributes of the same name.

The keytype IDL attribute must reflect the content attributes of the same name, limited to only known values.

The type IDL attribute must return the value "keygen".

This specification does not specify how the private key generated is to be used. It is expected that after receiving the SignedPublicKeyAndChallenge (SPKAC) structure, the server will generate a client certificate and offer it back to the user for download; this certificate, once downloaded and stored in the key store along with the private key, can then be used to authenticate to services that use SSL and certificate authentication.

To generate a key pair, add the private key to the user's key store, and submit the public key to the server, markup such as the following can be used:

<form action="processkey.cgi" method="post" enctype="multipart/form-data">
 <p><keygen name="key"></p>
 <p><input type=submit value="Submit key..."></p>
</form>

The server will then receive a form submission with a packaged RSA public key as the value of "key". This can then be used for various purposes, such as generating a client certificate, as mentioned above.

4.10.15 The `output` element

Status: Last call for comments

Categories

Listed, labelable, and resettable form-associated element.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Content attributes:

for

form

name

DOM interface:

interface HTMLOutputElement : HTMLElement {
  [PutForwards=value] readonly attribute DOMSettableTokenList htmlFor;
  readonly attribute HTMLFormElement form;
           attribute DOMString name;

  readonly attribute DOMString type;
           attribute DOMString defaultValue;
           attribute DOMString value;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);

  readonly attribute NodeList labels;
};

The output element represents the result of a calculation.

The for content attribute allows an explicit relationship to be made between the result of a calculation and the elements that represent the values that went into the calculation or that otherwise influenced the calculation. The for attribute, if specified, must contain a string consisting of an unordered set of unique space-separated tokens, each of which must have the value of an ID of an element in the same Document.

The form attribute is used to explicitly associate the output element with its form owner. The name attribute represents the element's name.

The element has a value mode flag which is either value or default. Initially, the value mode flag must be set to default.

When the value mode flag is in mode default, the contents of the element represent both the value of the element and its default value. When the value mode flag is in mode value, the contents of the element represent the value of the element only, and the default value is only accessible using the defaultValue IDL attribute.

The element also has a default value. Initially, the default value must be the empty string.

Whenever the element's descendants are changed in any way, if the value mode flag is in mode default, the element's default value must be set to the value of the element's textContent IDL attribute.

The reset algorithm for output elements is to set the element's textContent IDL attribute to the value of the element's defaultValue IDL attribute (thus replacing the element's child nodes), and then to set the element's value mode flag to default.

output . value [ = value ]

Returns the element's current value.

Can be set, to change the value.

output . defaultValue [ = value ]

Returns the element's current default value.

Can be set, to change the default value.

output . type

Returns the string "output".

The value IDL attribute must act like the element's textContent IDL attribute, except that on setting, in addition, before the child nodes are changed, the element's value mode flag must be set to value.

The defaultValue IDL attribute, on getting, must return the element's default value. On setting, the attribute must set the element's default value, and, if the element's value mode flag is in the mode default, set the element's textContent IDL attribute as well.

The type attribute must return the string "output".

The htmlFor IDL attribute must reflect the for content attribute.

Constraint validation: output elements are always barred from constraint validation.

A simple calculator could use output for its display of calculated results:

<form onsubmit="return false">
 <input name=a type=number step=any> +
 <input name=b type=number step=any> =
 <output onforminput="value = a.value + b.value"></output>
</form>

4.10.16 The `progress` element

Status: Last call for comments. ISSUE-96 (progress) blocks progress to Last Call

Categories

Labelable form-associated element.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Phrasing content, but there must be no progress element descendants.

Content attributes:

value

max

form

DOM interface:

interface HTMLProgressElement : HTMLElement {
           attribute float value;
           attribute float max;
  readonly attribute float position;
  readonly attribute HTMLFormElement form;
  readonly attribute NodeList labels;
};

The progress element represents the completion progress of a task. The progress is either indeterminate, indicating that progress is being made but that it is not clear how much more work remains to be done before the task is complete (e.g. because the task is waiting for a remote host to respond), or the progress is a number in the range zero to a maximum, giving the fraction of work that has so far been completed.

There are two attributes that determine the current task completion represented by the element.

The value attribute specifies how much of the task has been completed, and the max attribute specifies how much work the task requires in total. The units are arbitrary and not specified.

Authors are encouraged to also include the current value and the maximum value inline as text inside the element, so that the progress is made available to users of legacy user agents.

Here is a snippet of a Web application that shows the progress of some automated task:

<section>
 <h2>Task Progress</h2>
 <p>Progress: <progress id="p" max=100><span>0</span>%</progress></p>
 <script>
  var progressBar = document.getElementById('p');
  function updateProgress(newValue) {
    progressBar.value = newValue;
    progressBar.getElementsByTagName('span')[0].textContent = newValue;
  }
 </script>
</section>

(The updateProgress() method in this example would be called by some other code on the page to update the actual progress bar as the task progressed.)

The value and max attributes, when present, must have values that are valid floating point numbers. The value attribute, if present, must have a value equal to or greater than zero, and less than or equal to the value of the max attribute, if present, or 1.0, otherwise. The max attribute, if present, must have a value greater than zero.

The progress element is the wrong element to use for something that is just a gauge, as opposed to task progress. For instance, indicating disk space usage using progress would be inappropriate. Instead, the meter element is available for such use cases.

User agent requirements: If the value attribute is omitted, then the progress bar is an indeterminate progress bar. Otherwise, it is a determinate progress bar.

If the progress bar is a determinate progress bar and the element has a max attribute, the user agent must parse the max attribute's value according to the rules for parsing floating point number values. If this does not result in an error, and if the parsed value is greater than zero, then the maximum value of the progress bar is that value. Otherwise, if the element has no max attribute, or if it has one but parsing it resulted in an error, or if the parsed value was less than or equal to zero, then the maximum value of the progress bar is 1.0.

If the progress bar is a determinate progress bar, user agents must parse the value attribute's value according to the rules for parsing floating point number values. If this does not result in an error, and if the parsed value is less than the maximum value and greater than zero, then the current value of the progress bar is that parsed value. Otherwise, if the parsed value was greater than or equal to the maximum value, then the current value of the progress bar is the maximum value of the progress bar. Otherwise, if parsing the value attribute's value resulted in an error, or a number less than or equal to zero, then the current value of the progress bar is zero.

UA requirements for showing the progress bar: When representing a progress element to the user, the UA should indicate whether it is a determinate or indeterminate progress bar, and in the former case, should indicate the relative position of the current value relative to the maximum value.

The max and value IDL attributes must reflect the respective content attributes of the same name. When the relevant content attributes are absent, the IDL attributes must return zero.

The form attribute is used to explicitly associate the progress element with its form owner.

Constraint validation: progress elements are always barred from constraint validation.

progress . position

For a determinate progress bar (one with known current and maximum values), returns the result of dividing the current value by the maximum value.

For an indeterminate progress bar, returns −1.

If the progress bar is an indeterminate progress bar, then the position IDL attribute must return −1. Otherwise, it must return the result of dividing the current value by the maximum value.

The labels attribute provides a list of the element's labels.

4.10.17 The `meter` element

Status: Last call for comments. ISSUE-97 (meter) blocks progress to Last Call

Categories

Labelable form-associated element.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Phrasing content, but there must be no meter element descendants.

Content attributes:

value

min

max

low

high

optimum

form

DOM interface:

interface HTMLMeterElement : HTMLElement {
           attribute float value;
           attribute float min;
           attribute float max;
           attribute float low;
           attribute float high;
           attribute float optimum;
  readonly attribute HTMLFormElement form;
  readonly attribute NodeList labels;
};

The meter element represents a scalar measurement within a known range, or a fractional value; for example disk usage, the relevance of a query result, or the fraction of a voting population to have selected a particular candidate.

This is also known as a gauge.

The meter element should not be used to indicate progress (as in a progress bar). For that role, HTML provides a separate progress element.

The meter element also does not represent a scalar value of arbitrary range — for example, it would be wrong to use this to report a weight, or height, unless there is a known maximum value.

There are six attributes that determine the semantics of the gauge represented by the element.

The min attribute specifies the lower bound of the range, and the max attribute specifies the upper bound. The value attribute specifies the value to have the gauge indicate as the "measured" value.

The other three attributes can be used to segment the gauge's range into "low", "medium", and "high" parts, and to indicate which part of the gauge is the "optimum" part. The low attribute specifies the range that is considered to be the "low" part, and the high attribute specifies the range that is considered to be the "high" part. The optimum attribute gives the position that is "optimum"; if that is higher than the "high" value then this indicates that the higher the value, the better; if it's lower than the "low" mark then it indicates that lower values are better, and naturally if it is in between then it indicates that neither high nor low values are good.

Authoring requirements: The value attribute must be specified. The value, min, low, high, max, and optimum attributes, when present, must have values that are valid floating point numbers.

In addition, the attributes' values are further constrained:

Let value be the value attribute's number.

If the min attribute attribute is specified, then let minimum be that attribute's value; otherwise, let it be zero.

If the max attribute attribute is specified, then let maximum be that attribute's value; otherwise, let it be 1.0.

The following inequalities must hold, as applicable:

minimum ≤ value ≤ maximum
minimum ≤ low ≤ maximum (if low is specified)
minimum ≤ high ≤ maximum (if high is specified)
minimum ≤ optimum ≤ maximum (if optimum is specified)
low ≤ high (if both low and high are specified)

If no minimum or maximum is specified, then the range is assumed to be 0..1, and the value thus has to be within that range.

Authors are encouraged to include a textual representation of the gauge's state in the element's contents, for users of user agents that do not support the meter element.

The following examples show three gauges that would all be three-quarters full:

Storage space usage: <meter value=6 max=8>6 blocks used (out of 8 total)</meter>
Voter turnout: <meter value=0.75><img alt="75%" src="graph75.png"></meter>
Tickets sold: <meter min="0" max="100" value="75"></meter>

The following example is incorrect use of the element, because it doesn't give a range (and since the default maximum is 1, both of the gauges would end up looking maxed out):

<p>The grapefruit pie had a radius of <meter value=12>12cm</meter>
and a height of <meter value=2>2cm</meter>.</p> <!-- BAD! -->

Instead, one would either not include the meter element, or use the meter element with a defined range to give the dimensions in context compared to other pies:

<p>The grapefruit pie had a radius of 12cm and a height of
2cm.</p>
<dl>
 <dt>Radius: <dd> <meter min=0 max=20 value=12>12cm</meter>
 <dt>Height: <dd> <meter min=0 max=10 value=2>2cm</meter>
</dl>

There is no explicit way to specify units in the meter element, but the units may be specified in the title attribute in free-form text.

The example above could be extended to mention the units:

<dl>
 <dt>Radius: <dd> <meter min=0 max=20 value=12 title="centimeters">12cm</meter>
 <dt>Height: <dd> <meter min=0 max=10 value=2 title="centimeters">2cm</meter>
</dl>

User agent requirements: User agents must parse the min, max, value, low, high, and optimum attributes using the rules for parsing floating point number values.

User agents must then use all these numbers to obtain values for six points on the gauge, as follows. (The order in which these are evaluated is important, as some of the values refer to earlier ones.)

The minimum value

If the min attribute is specified and a value could be parsed out of it, then the minimum value is that value. Otherwise, the minimum value is zero.

The maximum value

If the max attribute is specified and a value could be parsed out of it, the maximum value is that value. Otherwise, the maximum value is 1.0.

If the maximum value would be less than the minimum value, then the maximum value is actually the same as the minimum value.

The actual value

If the value attribute is specified and a value could be parsed out of it, then that value is the actual value. Otherwise, the actual value is zero.

If the actual value would be less than the minimum value, then the actual value is actually the same as the minimum value.

If, on the other hand, the actual value would be greater than the maximum value, then the actual value is the maximum value.

The low boundary

If the low attribute is specified and a value could be parsed out of it, then the low boundary is that value. Otherwise, the low boundary is the same as the minimum value.

If the low boundary is then less than the minimum value, then the low boundary is actually the same as the minimum value. Similarly, if the low boundary is greater than the maximum value, then it is actually the maximum value instead.

The high boundary

If the high attribute is specified and a value could be parsed out of it, then the high boundary is that value. Otherwise, the high boundary is the same as the maximum value.

If the high boundary is then less than the low boundary, then the high boundary is actually the same as the low boundary. Similarly, if the high boundary is greater than the maximum value, then it is actually the maximum value instead.

The optimum point

If the optimum attribute is specified and a value could be parsed out of it, then the optimum point is that value. Otherwise, the optimum point is the midpoint between the minimum value and the maximum value.

If the optimum point is then less than the minimum value, then the optimum point is actually the same as the minimum value. Similarly, if the optimum point is greater than the maximum value, then it is actually the maximum value instead.

All of which will result in the following inequalities all being true:

minimum value ≤ actual value ≤ maximum value
minimum value ≤ low boundary ≤ high boundary ≤ maximum value
minimum value ≤ optimum point ≤ maximum value

UA requirements for regions of the gauge: If the optimum point is equal to the low boundary or the high boundary, or anywhere in between them, then the region between the low and high boundaries of the gauge must be treated as the optimum region, and the low and high parts, if any, must be treated as suboptimal. Otherwise, if the optimum point is less than the low boundary, then the region between the minimum value and the low boundary must be treated as the optimum region, the region between the low boundary and the high boundary must be treated as a suboptimal region, and the region between the high boundary and the maximum value must be treated as an even less good region. Finally, if the optimum point is higher than the high boundary, then the situation is reversed; the region between the high boundary and the maximum value must be treated as the optimum region, the region between the high boundary and the low boundary must be treated as a suboptimal region, and the remaining region between the low boundary and the minimum value must be treated as an even less good region.

UA requirements for showing the gauge: When representing a meter element to the user, the UA should indicate the relative position of the actual value to the minimum and maximum values, and the relationship between the actual value and the three regions of the gauge.

The following markup:

<h3>Suggested groups</h3>
<menu type="toolbar">
 <a href="?cmd=hsg" onclick="hideSuggestedGroups()">Hide suggested groups</a>
</menu>
<ul>
 <li>
  <p><a href="/group/comp.infosystems.www.authoring.stylesheets/view">comp.infosystems.www.authoring.stylesheets</a> -
     <a href="/group/comp.infosystems.www.authoring.stylesheets/subscribe">join</a></p>
  <p>Group description: <strong>Layout/presentation on the WWW.</strong></p>
  <p><meter value="0.5">Moderate activity,</meter> Usenet, 618 subscribers</p>
 </li>
 <li>
  <p><a href="/group/netscape.public.mozilla.xpinstall/view">netscape.public.mozilla.xpinstall</a> -
     <a href="/group/netscape.public.mozilla.xpinstall/subscribe">join</a></p>
  <p>Group description: <strong>Mozilla XPInstall discussion.</strong></p>
  <p><meter value="0.25">Low activity,</meter> Usenet, 22 subscribers</p>
 </li>
 <li>
  <p><a href="/group/mozilla.dev.general/view">mozilla.dev.general</a> -
     <a href="/group/mozilla.dev.general/subscribe">join</a></p>
  <p><meter value="0.25">Low activity,</meter> Usenet, 66 subscribers</p>
 </li>
</ul>

Might be rendered as follows:

With the <meter> elements rendered as inline green bars of varying lengths.

User agents may combine the value of the title attribute and the other attributes to provide context-sensitive help or inline text detailing the actual values.

For example, the following snippet:

<meter min=0 max=60 value=23.2 title=seconds></meter>

...might cause the user agent to display a gauge with a tooltip saying "Value: 23.2 out of 60." on one line and "seconds" on a second line.

The form attribute is used to explicitly associate the meter element with its form owner.

Constraint validation: meter elements are always barred from constraint validation.

The min, max, value, low, high, and optimum IDL attributes must reflect the respective content attributes of the same name. When the relevant content attributes are absent, the IDL attributes must return zero.

The labels attribute provides a list of the element's labels.

The following example shows how a gauge could fall back to localized or pretty-printed text.

<p>Disk usage: <meter min=0 value=170261928 max=233257824>170 261 928 bytes used
out of 233 257 824 bytes available</meter></p>

4.10.18 Association of controls and forms

Status: Last call for comments

A form-associated element can have a relationship with a form element, which is called the element's form owner. If a form-associated element is not associated with a form element, its form owner is said to be null.

A form-associated element is, by default, associated with its nearest ancestor form element (as described below), but may have a form attribute specified to override this.

If a form-associated element has a form attribute specified, then its value must be the ID of a form element in the element's owner Document.

When a form-associated element is created, its form owner must be initialized to null (no owner).

When a form-associated element is to be associated with a form, its form owner must be set to that form.

When a form-associated element's ancestor chain changes, e.g. because it or one of its ancestors was inserted or removed from a Document, then the user agent must reset the form owner of that element.

When a form-associated element's form attribute is added, removed, or has its value changed, then the user agent must reset the form owner of that element.

When a form-associated element has a form attribute and the ID of any of the form elements in the Document changes, then the user agent must reset the form owner of that form-associated element.

When the user agent is to reset the form owner of a form-associated element, it must run the following steps:

If the element's form owner is not null, and the element's form content attribute is not present, and the element's form owner is one of the ancestors of the element after the change to the ancestor chain, then do nothing, and abort these steps.
Let the element's form owner be null.
If the element has a form content attribute, then run these substeps:
1. If the first element in the Document to have an ID that is case-sensitively equal to the element's form content attribute's value is a form element, then associate the form-associated element with that form element.
2. Abort the "reset the form owner" steps.
Otherwise, if the form-associated element in question has an ancestor form element, then associate the form-associated element with the nearest such ancestor form element.
Otherwise, the element is left unassociated.

In the following non-conforming snippet:

...
 <form id="a">
  <div id="b"></div>
 </form>
 <script>
  document.getElementById('b').innerHTML =
     '<table><tr><td><form id="c"><input id="d"></table>' +
     '<input id="e">';
 </script>
...

The form owner of "d" would be the inner nested form "c", while the form owner of "e" would be the outer form "a".

This is because despite the association of "e" with "c" in the HTML parser, when the innerHTML algorithm moves the nodes from the temporary document to the "b" element, the nodes see their ancestor chain change, and thus all the "magic" associations done by the parser are reset to normal ancestor associations.

This example is a non-conforming document, though, as it is a violation of the content models to nest form elements.

element . form

Returns the element's form owner.

Returns null if there isn't one.

Form-associated elements have a form IDL attribute, which, on getting, must return the element's form owner, or null if there isn't one.

Constraint validation: If an element has no form owner, it is barred from constraint validation.

4.10.19 Attributes common to form controls

Status: Last call for comments

4.10.19.1 Naming form controls

Status: Last call for comments

The name content attribute gives the name of the form control, as used in form submission and in the form element's elements object. If the attribute is specified, its value must not be the empty string.

Constraint validation: If an element does not have a name attribute specified, or its name attribute's value is the empty string, then it is barred from constraint validation.

The name IDL attribute must reflect the name content attribute.

4.10.19.2 Enabling and disabling form controls

Status: Last call for comments

The disabled content attribute is a boolean attribute.

A form control is disabled if its disabled attribute is set, or if it is a descendant of a fieldset element whose disabled attribute is set and is not a descendant of that fieldset element's first legend element child, if any.

A form control that is disabled must prevent any click events that are queued on the user interaction task source from being dispatched on the element.

Constraint validation: If an element is disabled, it is barred from constraint validation.

The disabled IDL attribute must reflect the disabled content attribute.

4.10.19.3 A form control's value

Form controls have a value and a checkedness. (The latter is only used by input elements.) These are used to describe how the user interacts with the control.

4.10.19.4 Autofocusing a form control

Status: Last call for comments

The autofocus content attribute allows the user to indicate that a control is to be focused as soon as the page is loaded, allowing the user to just start typing without having to manually focus the main control.

The autofocus attribute is a boolean attribute.

There must not be more than one element in the document with the autofocus attribute specified.

Whenever an element with the autofocus attribute specified is inserted into a document, the user agent should queue a task that checks to see if the element is focusable, and if so, runs the focusing steps for that element. User agents may also change the scrolling position of the document, or perform some other action that brings the element to the user's attention. The task source for this task is the DOM manipulation task source.

User agents may ignore this attribute if the user has indicated (for example, by starting to type in a form control) that he does not wish focus to be changed.

Focusing the control does not imply that the user agent must focus the browser window if it has lost focus.

The autofocus IDL attribute must reflect the content attribute of the same name.

In the following snippet, the text control would be focused when the document was loaded.

<input maxlength="256" name="q" value="" autofocus>
<input type="submit" value="Search">

4.10.19.5 Limiting user input length

Status: Last call for comments

A form control maxlength attribute, controlled by a dirty value flag declares a limit on the number of characters a user can input.

If an element has its form control maxlength attribute specified, the attribute's value must be a valid non-negative integer. If the attribute is specified and applying the rules for parsing non-negative integers to its value results in a number, then that number is the element's maximum allowed value length. If the attribute is omitted or parsing its value results in an error, then there is no maximum allowed value length.

Constraint validation: If an element has a maximum allowed value length, and its dirty value flag is true, and the code-point length of the element's value is greater than the element's maximum allowed value length, then the element is suffering from being too long.

User agents may prevent the user from causing the element's value to be set to a value whose code-point length is greater than the element's maximum allowed value length.

4.10.19.6 Form submission

Status: Last call for comments

Attributes for form submission can be specified both on form elements and on submit buttons (elements that represent buttons that submit forms, e.g. an input element whose type attribute is in the Submit Button state).

The attributes for form submission that may be specified on form elements are action, enctype, method, novalidate, and target.

The corresponding attributes for form submission that may be specified on submit buttons are formaction, formenctype, formmethod, formnovalidate, and formtarget. When omitted, they default to the values given on the corresponding attributes on the form element.

The action and formaction content attributes, if specified, must have a value that is a valid URL.

The action of an element is the value of the element's formaction attribute, if the element is a submit button and has such an attribute, or the value of its form owner's action attribute, if it has one, or else the empty string.

The method and formmethod content attributes are enumerated attributes with the following keywords and states:

The keyword GET, mapping to the state GET, indicating the HTTP GET method.
The keyword POST, mapping to the state POST, indicating the HTTP POST method.
The keyword PUT, mapping to the state PUT, indicating the HTTP PUT method.
The keyword DELETE, mapping to the state DELETE, indicating the HTTP DELETE method.

The missing value default for these attributes is the GET state.

The method of an element is one of those four states. If the element is a submit button and has a formmethod attribute, then the element's method is that attribute's state; otherwise, it is the form owner's method attribute's state.

The enctype and formenctype content attributes are enumerated attributes with the following keywords and states:

The "application/x-www-form-urlencoded" keyword and corresponding state.
The "multipart/form-data" keyword and corresponding state.
The "text/plain" keyword and corresponding state.

The missing value default for these attributes is the application/x-www-form-urlencoded state.

The enctype of an element is one of those three states. If the element is a submit button and has a formenctype attribute, then the element's enctype is that attribute's state; otherwise, it is the form owner's enctype attribute's state.

The target and formtarget content attributes, if specified, must have values that are valid browsing context names or keywords.

The target of an element is the value of the element's formtarget attribute, if the element is a submit button and has such an attribute; or the value of its form owner's target attribute, if it has such an attribute; or, if one of the child nodes of the head element is a base element with a target attribute, then the value of the target attribute of the first such base element; or, if there is no such element, the empty string.

The novalidate and formnovalidate content attributes are boolean attributes. If present, they indicate that the form is not to be validated during submission.

The no-validate state of an element is true if the element is a submit button and the element's formnovalidate attribute is present, or if the element's form owner's novalidate attribute is present, and false otherwise.

This attribute is useful to include "save" buttons on forms that have validation constraints, to allow users to save their progress even though they haven't fully entered the data in the form. The following example shows a simple form that has two required fields. There are three buttons: one to submit the form, which requires both fields to be filled in; one to save the form so that the user can come back and fill it in later; and one to cancel the form altogether.

<form action="editor.cgi" method="post">
 <p><label>Name: <input required name=fn></label></p>
 <p><label>Essay: <textarea name=essay></textarea></label></p>
 <p><input type=submit name=submit value="Submit essay"></p>
 <p><input type=submit formnovalidate name=save value="Save essay"></p>
 <p><input type=submit formnovalidate name=cancel value="Cancel"></p>
</form>

The action, method, enctype, and target IDL attributes must reflect the respective content attributes of the same name. The noValidate IDL attribute must reflect the novalidate content attribute. The formAction IDL attribute must reflect the formaction content attribute. The formEnctype IDL attribute must reflect the formenctype content attribute. The formMethod IDL attribute must reflect the formmethod content attribute. The formNoValidate IDL attribute must reflect the formnovalidate content attribute. The formTarget IDL attribute must reflect the formtarget content attribute.

4.10.20 Constraints

Status: Last call for comments

4.10.20.1 Definitions

Status: Last call for comments

A listed form-associated element is a candidate for constraint validation except when a condition has barred the element from constraint validation. (For example, an element is barred from constraint validation if it is an output or fieldset element.)

An element can have a custom validity error message defined. Initially, an element must have its custom validity error message set to the empty string. When its value is not the empty string, the element is suffering from a custom error. It can be set using the setCustomValidity() method. The user agent should use the custom validity error message when alerting the user to the problem with the control.

An element can be constrained in various ways. The following is the list of validity states that a form control can be in, making the control invalid for the purposes of constraint validation. (The definitions below are non-normative; other parts of this specification define more precisely when each state applies or does not.)

Suffering from being missing: When a control has no value but has a required attribute (input required, textarea required).
Suffering from a type mismatch: When a control that allows arbitrary user input has a value that is not in the correct syntax (E-mail, URL).
Suffering from a pattern mismatch: When a control has a value that doesn't satisfy the pattern attribute.
Suffering from being too long: When a control has a value that is too long for the form control maxlength attribute (input maxlength, textarea maxlength).
Suffering from an underflow: When a control has a value that is too low for the min attribute.
Suffering from an overflow: When a control has a value that is too high for the max attribute.
Suffering from a step mismatch: When a control has a value that doesn't fit the rules given by the step attribute.
Suffering from a custom error: When a control's custom validity error message (as set by the element's setCustomValidity() method) is not the empty string.

An element can still suffer from these states even when the element is disabled; thus these states can be represented in the DOM even if validating the form during submission wouldn't indicate a problem to the user.

An element satisfies its constraints if it is not suffering from any of the above validity states.

4.10.20.2 Constraint validation

Status: Last call for comments

When the user agent is required to statically validate the constraints of form element form, it must run the following steps, which return either a positive result (all the controls in the form are valid) or a negative result (there are invalid controls) along with a (possibly empty) list of elements that are invalid and for which no script has claimed responsibility:

Let controls be a list of all the submittable elements whose form owner is form, in tree order.
Let invalid controls be an initially empty list of elements.
For each element field in controls, in tree order, run the following substeps:
1. If field is not a candidate for constraint validation, then move on to the next element.
2. Otherwise, if field satisfies its constraints, then move on to the next element.
3. Otherwise, add field to invalid controls.
If invalid controls is empty, then return a positive result and abort these steps.
Let unhandled invalid controls be an initially empty list of elements.
For each element field in invalid controls, if any, in tree order, run the following substeps:
1. Fire a simple event named invalid that is cancelable at field.
2. If the event was not canceled, then add field to unhandled invalid controls.
Return a negative result with the list of elements in the unhandled invalid controls list.

If a user agent is to interactively validate the constraints of form element form, then the user agent must run the following steps:

Statically validate the constraints of form, and let unhandled invalid controls be the list of elements returned if the result was negative.
If the result was positive, then return that result and abort these steps.
Report the problems with the constraints of at least one of the elements given in unhandled invalid controls to the user. User agents may focus one of those elements in the process, by running the focusing steps for that element, and may change the scrolling position of the document, or perform some other action that brings the element to the user's attention. User agents may report more than one constraint violation. User agents may coalesce related constraint violation reports if appropriate (e.g. if multiple radio buttons in a group are marked as required, only one error need be reported). If one of the controls is not being rendered (e.g. it has the hidden attribute set) then user agents may report a script error.
Return a negative result.

4.10.20.3 The constraint validation API

Status: Last call for comments

element . willValidate

Returns true if the element will be validated when the form is submitted; false otherwise.

element . setCustomValidity(message)

Sets a custom error, so that the element would fail to validate. The given message is the message to be shown to the user when reporting the problem to the user.

If the argument is the empty string, clears the custom error.

element . validity . valueMissing

Returns true if the element has no value but is a required field; false otherwise.

element . validity . typeMismatch

Returns true if the element's value is not in the correct syntax; false otherwise.

element . validity . patternMismatch

Returns true if the element's value doesn't match the provided pattern; false otherwise.

element . validity . tooLong

Returns true if the element's value is longer than the provided maximum length; false otherwise.

element . validity . rangeUnderflow

Returns true if the element's value is lower than the provided minimum; false otherwise.

element . validity . rangeOverflow

Returns true if the element's value is higher than the provided maximum; false otherwise.

element . validity . stepMismatch

Returns true if the element's value doesn't fit the rules given by the step attribute; false otherwise.

element . validity . customError

Returns true if the element has a custom error; false otherwise.

element . validity . valid

Returns true if the element's value has no validity problems; false otherwise.

valid = element . checkValidity()

Returns true if the element's value has no validity problems; false otherwise. Fires an invalid event at the element in the latter case.

element . validationMessage

Returns the error message that would be shown to the user if the element was to be checked for validity.

The willValidate attribute must return true if an element is a candidate for constraint validation, and false otherwise (i.e. false if any conditions are barring it from constraint validation).

The setCustomValidity(message), when invoked, must set the custom validity error message to the value of the given message argument.

In the following example, a script checks the value of a form control each time it is edited, and whenever it is not a valid value, uses the setCustomValidity() method to set an appropriate message.

<label>Feeling: <input name=f type="text" oninput="check(this)"></label>
<script>
 function check(input) {
   if (input.value == "good" ||
       input.value == "fine" ||
       input.value == "tired") {
     input.setCustomValidity('"' + input.value + '" is not a feeling.');
   } else {
     // input is fine -- reset the error message
     input.setCustomValidity('');
   }
 }
</script>

The validity attribute must return a ValidityState object that represents the validity states of the element. This object is live, and the same object must be returned each time the element's validity attribute is retrieved.

interface ValidityState {
  readonly attribute boolean valueMissing;
  readonly attribute boolean typeMismatch;
  readonly attribute boolean patternMismatch;
  readonly attribute boolean tooLong;
  readonly attribute boolean rangeUnderflow;
  readonly attribute boolean rangeOverflow;
  readonly attribute boolean stepMismatch;
  readonly attribute boolean customError;
  readonly attribute boolean valid;
};

A ValidityState object has the following attributes. On getting, they must return true if the corresponding condition given in the following list is true, and false otherwise.

valueMissing: The control is suffering from being missing.
typeMismatch: The control is suffering from a type mismatch.
patternMismatch: The control is suffering from a pattern mismatch.
tooLong: The control is suffering from being too long.
rangeUnderflow: The control is suffering from an underflow.
rangeOverflow: The control is suffering from an overflow.
stepMismatch: The control is suffering from a step mismatch.
customError: The control is suffering from a custom error.
valid: None of the other conditions are true.

When the checkValidity() method is invoked, if the element is a candidate for constraint validation and does not satisfy its constraints, the user agent must fire a simple event named invalid that is cancelable (but in this case has no default action) at the element and return false. Otherwise, it must only return true without doing anything else.

The validationMessage attribute must return the empty string if the element is not a candidate for constraint validation or if it is one but it satisfies its constraints; otherwise, it must return a suitably localized message that the user agent would show the user if this were the only form control with a validity constraint problem. If the element is a candidate for constraint validation and is suffering from a custom error, then the custom validity error message should be present in the return value.

4.10.20.4 Security

Status: Last call for comments

Servers should not rely on client-side validation. Client-side validation can be intentionally bypassed by hostile users, and unintentionally bypassed by users of older user agents or automated tools that do not implement these features. The constraint validation features are only intended to improve the user experience, not to provide any kind of security mechanism.

4.10.21 Form submission

Status: Last call for comments

4.10.21.1 Introduction

Status: Last call for comments

This section is non-normative.

When forms are submitted, the data in the form is converted into the form specified by the enctype, and then sent to the destination specified by the action using the given method.

For example, take the following form:

<form action="/find.cgi" method=get>
 <input type=text name=t>
 <input type=search name=q>
 <input type=submit>
</form>

If the user types in "cats" in the first field and "fur" in the second, and then hits the submit button, then the user agent will load /find.cgi?t=cats&q=fur.

On the other hand, consider this form:

<form action="/find.cgi" method=post enctype="multipart/form-data">
 <input type=text name=t>
 <input type=search name=q>
 <input type=submit>
</form>

Given the same user input, the result on submission is quite different: the user agent instead does an HTTP POST to the given URL, with as the entity body something like the following text:

------kYFrd4jNJEgCervE
Content-Disposition: form-data; name="t"

cats
------kYFrd4jNJEgCervE
Content-Disposition: form-data; name="q"

fur
------kYFrd4jNJEgCervE--

4.10.21.2 Implicit submission

Status: Last call for comments

User agents may establish a button in each form as being the form's default button. This should be the first submit button in tree order whose form owner is that form element, but user agents may pick another button if another would be more appropriate for the platform. If the platform supports letting the user submit a form implicitly (for example, on some platforms hitting the "enter" key while a text field is focused implicitly submits the form), then doing so must cause the form's default button's activation behavior, if any, to be run.

Consequently, if the default button is disabled, the form is not submitted when such an implicit submission mechanism is used. (A button has no activation behavior when disabled.)

If the form has no submit button, then the implicit submission mechanism must just submit the form element from the form element itself.

4.10.21.3 Form submission algorithm

Status: Last call for comments

When a form form is submitted from an element submitter (typically a button), optionally with a scripted-submit flag set, the user agent must run the following steps:

If form is in a Document that has no associated browsing context or whose browsing context had its sandboxed forms browsing context flag set when the Document was created, then abort these steps without doing anything.
If form is already being submitted (i.e. the form was submitted again while processing the events fired from the next two steps, probably from a script redundantly calling the submit() method on form), then abort these steps. This doesn't affect the earlier instance of this algorithm.
If the scripted-submit flag is not set, and the submitter element's no-validate state is false, then interactively validate the constraints of form and examine the result: if the result is negative (the constraint validation concluded that there were invalid fields and probably informed the user of this) then abort these steps.
If the scripted-submit flag is not set, then fire a simple event that is cancelable named submit, at form. If the event's default action is prevented (i.e. if the event is canceled) then abort these steps. Otherwise, continue (effectively the default action is to perform the submission).
Let controls be a list of all the submittable elements whose form owner is form, in tree order.
Let the form data set be a list of name-value-type tuples, initially empty.
Constructing the form data set. For each element field in controls, in tree order, run the following substeps:
1. If any of the following conditions are met, then skip these substeps for this element:
  - The field element has a datalist element ancestor.
  - The field element is disabled.
  - The field element is a button but it is not submitter.
  - The field element is an input element whose type attribute is in the Checkbox state and whose checkedness is false.
  - The field element is an input element whose type attribute is in the Radio Button state and whose checkedness is false.
  - The field element is an input element whose type attribute is in the File Upload state but the control does not have any files selected.
  - The field element is an object element that is not using a plugin.
  Otherwise, process field as follows:
2. Let type be the value of the type IDL attribute of field.
3. If the field element is an input element whose type attribute is in the Image Button state, then run these further nested substeps:
  1. If the field element has an name attribute specified and value is not the empty string, let name be that value followed by a single U+002E FULL STOP character (.). Otherwise, let name be the empty string.
  2. Let name_x be the string consisting of the concatenation of name and a single U+0078 LATIN SMALL LETTER X character (x).
  3. Let name_y be the string consisting of the concatenation of name and a single U+0079 LATIN SMALL LETTER Y character (y).
  4. The field element is submitter, and before this algorithm was invoked the user indicated a coordinate. Let x be the x-component of the coordinate selected by the user, and let y be the y-component of the coordinate selected by the user.
  5. Append an entry in the form data set with the name name_x, the value x, and the type type.
  6. Append an entry in the form data set with the name name_y and the value y, and the type type.
  7. Skip the remaining substeps for this element: if there are any more elements in controls, return to the top of the constructing the form data set step, otherwise, jump to the next step in the overall form submission algorithm.
4. If the field element does not have a name attribute specified, or its name attribute's value is the empty string, skip these substeps for this element: if there are any more elements in controls, return to the top of the constructing the form data set step, otherwise, jump to the next step in the overall form submission algorithm.
5. Let name be the value of the field element's name attribute.
6. If the field element is a select element, then for each option element in the select element whose selectedness is true, append an entry in the form data set with the name as the name, the value of the option element as the value, and type as the type.
7. Otherwise, if the field element is an input element whose type attribute is in the Checkbox state or the Radio Button state, then run these further nested substeps:
  1. If the field element has a value attribute specified, then let value be the value of that attribute; otherwise, let value be the string "on".
  2. Append an entry in the form data set with name as the name, value as the value, and type as the type.
8. Otherwise, if the field element is an input element whose type attribute is in the File Upload state, then for each file selected in the input element, append an entry in the form data set with the name as the name, the file (consisting of the name, the type, and the body) as the value, and type as the type.
9. Otherwise, if the field element is an object element: try to obtain a form submission value from the plugin, and if that is successful, append an entry in the form data set with name as the name, the returned form submission value as the value, and the string "object" as the type.
10. Otherwise, append an entry in the form data set with name as the name, the value of the field element as the value, and type as the type.
Let action be the submitter element's action.
If action is the empty string, let action be the document's address.

This step is a willful violation of RFC 3986, which would require base URL processing here. This violation is motivated by a desire for compatibility with legacy content. [RFC3986]
Resolve the URL action, relative to the submitter element. If this fails, abort these steps. Otherwise, let action be the resulting absolute URL.
Let scheme be the <scheme> of the resulting absolute URL.
Let enctype be the submitter element's enctype.
Let method be the submitter element's method.
Let target be the submitter element's target.

Select the appropriate row in the table below based on the value of scheme as given by the first cell of each row. Then, select the appropriate cell on that row based on the value of method as given in the first cell of each column. Then, jump to the steps named in that cell and defined below the table.

	GET	POST	PUT	DELETE
`http`	Mutate action	Submit as entity body	Submit as entity body	Delete action
`https`	Mutate action	Submit as entity body	Submit as entity body	Delete action
`ftp`	Get action	Get action	Get action	Get action
`javascript`	Get action	Get action	Get action	Get action
`data`	Get action	Post to data:	Put to data:	Get action
`mailto`	Mail with headers	Mail as body	Mail with headers	Mail with headers

If scheme is not one of those listed in this table, then the behavior is not defined by this specification. User agents should, in the absence of another specification defining this, act in a manner analogous to that defined in this specification for similar schemes.

The behaviors are as follows:

Mutate action

Let query be the result of encoding the form data set using the application/x-www-form-urlencoded encoding algorithm, interpreted as a US-ASCII string.

Let destination be a new URL that is equal to the action except that its <query> component is replaced by query (adding a U+003F QUESTION MARK character (?) if appropriate).

Let target browsing context be the form submission target browsing context.

Navigate target browsing context to destination. If target browsing context was newly created for this purpose by the steps above, then it must be navigated with replacement enabled.

Submit as entity body

Let entity body be the result of encoding the form data set using the appropriate form encoding algorithm.

Let target browsing context be the form submission target browsing context.

Let MIME type be determined as follows:

If enctype is application/x-www-form-urlencoded: Let MIME type be "application/x-www-form-urlencoded".
If enctype is multipart/form-data: Let MIME type be "multipart/form-data".
If enctype is text/plain: Let MIME type be "text/plain".

If method is anything but GET or POST, and the origin of action is not the same origin as that of the form element's Document, then abort these steps.

Otherwise, navigate target browsing context to action using the HTTP method given by method and with entity body as the entity body, of type MIME type. If target browsing context was newly created for this purpose by the steps above, then it must be navigated with replacement enabled.

Delete action

Let target browsing context be the form submission target browsing context.

If the origin of action is not the same origin as that of the form element's Document, then abort these steps.

Otherwise, navigate target browsing context to action using the DELETE method. If target browsing context was newly created for this purpose by the steps above, then it must be navigated with replacement enabled.

Get action

Let target browsing context be the form submission target browsing context.

Navigate target browsing context to action. If target browsing context was newly created for this purpose by the steps above, then it must be navigated with replacement enabled.

Post to data:

Let data be the result of encoding the form data set using the appropriate form encoding algorithm.

If action contains the string "%%%%" (four U+0025 PERCENT SIGN characters), then %-escape all bytes in data that, if interpreted as US-ASCII, do not match the unreserved production in the URI Generic Syntax, and then, treating the result as a US-ASCII string, further %-escape all the U+0025 PERCENT SIGN characters in the resulting string and replace the first occurrence of "%%%%" in action with the resulting double-escaped string. [RFC3986]

Otherwise, if action contains the string "%%" (two U+0025 PERCENT SIGN characters in a row, but not four), then %-escape all characters in data that, if interpreted as US-ASCII, do not match the unreserved production in the URI Generic Syntax, and then, treating the result as a US-ASCII string, replace the first occurrence of "%%" in action with the resulting escaped string. [RFC3986]

Let target browsing context be the form submission target browsing context.

Navigate target browsing context to the potentially modified action. If target browsing context was newly created for this purpose by the steps above, then it must be navigated with replacement enabled.

Put to data:

Let data be the result of encoding the form data set using the appropriate form encoding algorithm.

Let MIME type be determined as follows:

If enctype is application/x-www-form-urlencoded: Let MIME type be "application/x-www-form-urlencoded".
If enctype is multipart/form-data: Let MIME type be "multipart/form-data".
If enctype is text/plain: Let MIME type be "text/plain".

Let destination be the result of concatenating the following:

The string "data:".
The value of MIME type.
The string ";base64,".
A base-64 encoded representation of data. [RFC2045]

Let target browsing context be the form submission target browsing context.

Navigate target browsing context to destination. If target browsing context was newly created for this purpose by the steps above, then it must be navigated with replacement enabled.

Mail with headers

Let headers be the resulting encoding the form data set using the application/x-www-form-urlencoded encoding algorithm, interpreted as a US-ASCII string.

Replace occurrences of U+002B PLUS SIGN characters (+) in headers with the string "%20".

Let destination consist of all the characters from the first character in action to the character immediately before the first U+003F QUESTION MARK character (?), if any, or the end of the string if there are none.

Append a single U+003F QUESTION MARK character (?) to destination.

Append headers to destination.

Let target browsing context be the form submission target browsing context.

Navigate target browsing context to destination. If target browsing context was newly created for this purpose by the steps above, then it must be navigated with replacement enabled.

Mail as body

Let body be the resulting encoding the form data set using the appropriate form encoding algorithm and then %-escaping all the bytes in the resulting byte string that, when interpreted as US-ASCII, do not match the unreserved production in the URI Generic Syntax. [RFC3986]

Let destination have the same value as action.

If destination does not contain a U+003F QUESTION MARK character (?), append a single U+003F QUESTION MARK character (?) to destination. Otherwise, append a single U+0026 AMPERSAND character (&).

Append the string "body=" to destination.

Append body, interpreted as a US-ASCII string, to destination.

Let target browsing context be the form submission target browsing context.

Navigate target browsing context to destination. If target browsing context was newly created for this purpose by the steps above, then it must be navigated with replacement enabled.

The form submission target browsing context is obtained, when needed by the behaviors described above, as follows: If the user indicated a specific browsing context to use when submitting the form, then that is the target browsing context. Otherwise, apply the rules for choosing a browsing context given a browsing context name using target as the name and the browsing context of form as the context in which the algorithm is executed; the resulting browsing context is the target browsing context.

The appropriate form encoding algorithm is determined as follows:

If enctype is application/x-www-form-urlencoded: Use the application/x-www-form-urlencoded encoding algorithm.
If enctype is multipart/form-data: Use the multipart/form-data encoding algorithm.
If enctype is text/plain: Use the text/plain encoding algorithm.

4.10.21.4 URL-encoded form data

Status: Last call for comments

The application/x-www-form-urlencoded encoding algorithm is as follows:

Let result be the empty string.
If the form element has an accept-charset attribute, then, taking into account the characters found in the form data set's names and values, and the character encodings supported by the user agent, select a character encoding from the list given in the form's accept-charset attribute that is an ASCII-compatible character encoding. If none of the encodings are supported, then let the selected character encoding be UTF-8.

Otherwise, if the document's character encoding is an ASCII-compatible character encoding, then that is the selected character encoding.

Otherwise, let the selected character encoding be UTF-8.
Let charset be the preferred MIME name of the selected character encoding.
For each entry in the form data set, perform these substeps:
1. If the entry's name is "_charset_" and its type is "hidden", replace its value with charset.
2. If the entry's type is "file", replace its value with the file's filename only.
3. For each character in the entry's name and value that cannot be expressed using the selected character encoding, replace the character by a string consisting of a U+0026 AMPERSAND character (&), a U+0023 NUMBER SIGN character (#), one or more characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9) representing the Unicode code point of the character in base ten, and finally a U+003B SEMICOLON character (;).
4. For each character in the entry's name and value, apply the following subsubsteps:
  1. If the character isn't in the range U+0020, U+002A, U+002D, U+002E, U+0030 to U+0039, U+0041 to U+005A, U+005F, U+0061 to U+007A then replace the character with a string formed as follows: Start with the empty string, and then, taking each byte of the character when expressed in the selected character encoding in turn, append to the string a U+0025 PERCENT SIGN character (%) followed by two characters in the ranges U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9) and U+0041 LATIN CAPITAL LETTER A to U+0046 LATIN CAPITAL LETTER F representing the hexadecimal value of the byte (zero-padded if necessary).
  2. If the character is a U+0020 SPACE character, replace it with a single U+002B PLUS SIGN character (+).
5. If the entry's name is "isindex", its type is "text", and this is the first entry in the form data set, then append the value to result and skip the rest of the substeps for this entry, moving on to the next entry, if any, or the next step in the overall algorithm otherwise.
6. If this is not the first entry, append a single U+0026 AMPERSAND character (&) to result.
7. Append the entry's name to result.
8. Append a single U+003D EQUALS SIGN character (=) to result.
9. Append the entry's value to result.
Encode result as US-ASCII and return the resulting byte stream.

4.10.21.5 Multipart form data

Status: Last call for comments

The multipart/form-data encoding algorithm is to encode the form data set using the rules described by RFC2388, Returning Values from Forms: multipart/form-data, and return the resulting byte stream. [RFC2388]

Each entry in the form data set is a field, the name of the entry is the field name and the value of the entry is the field value.

The order of parts must be the same as the order of fields in the form data set. Multiple entries with the same name must be treated as distinct fields.

4.10.21.6 Plain text form data

Status: Last call for comments

The text/plain encoding algorithm is as follows:

Let result be the empty string.
If the form element has an accept-charset attribute, then, taking into account the characters found in the form data set's names and values, and the character encodings supported by the user agent, select a character encoding from the list given in the form's accept-charset attribute. If none of the encodings are supported, then let the selected character encoding be UTF-8.

Otherwise, the selected character encoding is the document's character encoding.
Let charset be the preferred MIME name of the selected character encoding.
If the entry's name is "_charset_" and its type is "hidden", replace its value with charset.
If the entry's type is "file", replace its value with the file's filename only.
For each entry in the form data set, perform these substeps:
1. Append the entry's name to result.
2. Append a single U+003D EQUALS SIGN character (=) to result.
3. Append the entry's value to result.
4. Append a U+000D CARRIAGE RETURN (CR) U+000A LINE FEED (LF) character pair to result.
Encode result using the selected character encoding and return the resulting byte stream.

4.10.22 Resetting a form

Status: Last call for comments

When a form form is reset, the user agent must fire a simple event named reset, that is cancelable, at form, and then, if that event is not canceled, must invoke the reset algorithm of each resettable elements whose form owner is form, and broadcast formchange events from form.

Each resettable element defines its own reset algorithm. Changes made to form controls as part of these algorithms do not count as changes caused by the user (and thus, e.g., do not cause input events to fire).

4.10.23 Event dispatch

Status: Last call for comments

When the user agent is to broadcast forminput events or broadcast formchange events from a form element form, it must run the following steps:

Let controls be a list of all the resettable elements whose form owner is form.
If the user agent was to broadcast forminput events, let event name be forminput. Otherwise the user agent was to broadcast formchange events; let event name be formchange.
For each element in controls, in tree order, fire a simple event named event name at the element.

4.11 Interactive elements

Status: Last call for comments

4.11.1 The `details` element

Status: Last call for comments. ISSUE-93 (details) blocks progress to Last Call

Categories

Contexts in which this element may be used:

Where flow content is expected.

Content model:

One summary element followed by flow content.

Content attributes:

open

DOM interface:

interface HTMLDetailsElement : HTMLElement {
           attribute boolean open;
};

The details element represents a disclosure widget from which the user can obtain additional information or controls.

The details element is not appropriate for footnotes. Please see the section on footnotes for details on how to mark up footnotes.

The first summary element child of the element, if any, represents the summary or legend of the details. If there is no child summary element, the user agent should provide its own legend (e.g. "Details").

The open content attribute is a boolean attribute. If present, it indicates that the details are to be shown to the user. If the attribute is absent, the details are not to be shown.

If the attribute is removed, then the details should be hidden. If the attribute is added, the details should be shown.

The user agent should allow the user to request that the details be shown or hidden. To honor a request for the details to be shown, the user agent must set the open attribute on the element to the value open. To honor a request for the details to be hidden, the user agent must remove the open attribute from the element.

The open attribute must reflect the open content attribute.

The following example shows the details element being used to hide technical details in a progress report.

<section class="progress window">
 <h1>Copying "Really Achieving Your Childhood Dreams"</h1>
 <details>
  <summary>Copying... <progress max="375505392" value="97543282"></progress> 25%</summary>
  <dl>
   <dt>Transfer rate:</dt> <dd>452KB/s</dd>
   <dt>Local filename:</dt> <dd>/home/rpausch/raycd.m4v</dd>
   <dt>Remote filename:</dt> <dd>/var/www/lectures/raycd.m4v</dd>
   <dt>Duration:</dt> <dd>01:16:27</dd>
   <dt>Color profile:</dt> <dd>SD (6-1-6)</dd>
   <dt>Dimensions:</dt> <dd>320×240</dd>
  </dl>
 </details>
</section>

The following shows how a details element can be used to hide some controls by default:

<details>
 <summary>Name & Extension:</summary>
 <p><input type=text name=fn value="Pillar Magazine.pdf">
 <p><label><input type=checkbox name=ext checked> Hide extension</label>
</details>

One could use this in conjuction with other details in a list to allow the user to collapse a set of fields down to a small set of headings, with the ability to open each one.

In these examples, the summary really just summarises what the controls can change, and not the actual values, which is less than ideal.

4.11.2 The `summary` element

Categories: None.
Contexts in which this element may be used:: As the first child of a details element.
Content model:: Phrasing content.
Content attributes:: Global attributes
DOM interface:: Uses HTMLElement.

The summary element represents a summary, caption, or legend for the rest of the contents of the summary element's parent details element, if any.

4.11.3 The `command` element

Status: Last call for comments

Categories

Contexts in which this element may be used:

Where metadata content is expected.

Where phrasing content is expected.

Content model:

Empty.

Content attributes:

type

label

icon

disabled

checked

radiogroup

Also, the title attribute has special semantics on this element.

DOM interface:

interface HTMLCommandElement : HTMLElement {
           attribute DOMString type;
           attribute DOMString label;
           attribute DOMString icon;
           attribute boolean disabled;
           attribute boolean checked;
           attribute DOMString radiogroup;
};

The command element represents a command that the user can invoke.

The type attribute indicates the kind of command: either a normal command with an associated action, or a state or option that can be toggled, or a selection of one item from a list of items.

The attribute is an enumerated attribute with three keywords and states. The "command" keyword maps to the Command state, the "checkbox" keyword maps to the Checkbox state, and the "radio" keyword maps to the Radio state. The missing value default is the Command state.

The Command state: The element represents a normal command with an associated action.
The Checkbox state: The element represents a state or option that can be toggled.
The Radio state: The element represents a selection of one item from a list of items.

The label attribute gives the name of the command, as shown to the user. The label attribute must be specified and must have a value that is not the empty string.

The title attribute gives a hint describing the command, which might be shown to the user to help him.

The icon attribute gives a picture that represents the command. If the attribute is specified, the attribute's value must contain a valid URL. To obtain the absolute URL of the icon, the attribute's value must be resolved relative to the element.

The disabled attribute is a boolean attribute that, if present, indicates that the command is not available in the current state.

The distinction between disabled and hidden is subtle. A command would be disabled if, in the same context, it could be enabled if only certain aspects of the situation were changed. A command would be marked as hidden if, in that situation, the command will never be enabled. For example, in the context menu for a water faucet, the command "open" might be disabled if the faucet is already open, but the command "eat" would be marked hidden since the faucet could never be eaten.

The checked attribute is a boolean attribute that, if present, indicates that the command is selected. The attribute must be omitted unless the type attribute is in either the Checkbox state or the Radio state.

The radiogroup attribute gives the name of the group of commands that will be toggled when the command itself is toggled, for commands whose type attribute has the value "radio". The scope of the name is the child list of the parent element. The attribute must be omitted unless the type attribute is in the Radio state.

The type, label, icon, disabled, checked, and radiogroup IDL attributes must reflect the respective content attributes of the same name.

The element's activation behavior depends on the value of the type attribute of the element, as follows:

If the type attribute is in the Checkbox state

If the element has a checked attribute, the UA must remove that attribute. Otherwise, the UA must add a checked attribute, with the literal value checked. The UA must then fire a click event at the element.

If the type attribute is in the Radio state

If the element has a parent, then the UA must walk the list of child nodes of that parent element, and for each node that is a command element, if that element has a radiogroup attribute whose value exactly matches the current element's (treating missing radiogroup attributes as if they were the empty string), and has a checked attribute, must remove that attribute.

Then, the element's checked attribute attribute must be set to the literal value checked and the user agent must fire a click event at the element.

Otherwise

The element has no activation behavior.

Firing a synthetic click event at the element does not cause any of the actions described above to happen.

command elements are not rendered unless they form part of a menu.

Here is an example of a toolbar with three buttons that let the user toggle between left, center, and right alignment. One could imagine such a toolbar as part of a text editor. The toolbar also has a separator followed by another button labeled "Publish", though that button is disabled.

<menu type="toolbar">
 <command type="radio" radiogroup="alignment" checked="checked"
          label="Left" icon="icons/alL.png" onclick="setAlign('left')">
 <command type="radio" radiogroup="alignment"
          label="Center" icon="icons/alC.png" onclick="setAlign('center')">
 <command type="radio" radiogroup="alignment"
          label="Right" icon="icons/alR.png" onclick="setAlign('right')">
 <hr>
 <command type="command" disabled
          label="Publish" icon="icons/pub.png" onclick="publish()">
</menu>

4.11.4 The `menu` element

Status: Last call for comments

Categories

If the element's type attribute is in the toolbar state: Interactive content.

Contexts in which this element may be used:

Where flow content is expected.

Content model:

Either: Zero or more li elements.

Or: Flow content.

Content attributes:

type

label

DOM interface:

interface HTMLMenuElement : HTMLElement {
           attribute DOMString type;
           attribute DOMString label;
};

The menu element represents a list of commands.

The type attribute is an enumerated attribute indicating the kind of menu being declared. The attribute has three states. The context keyword maps to the context menu state, in which the element is declaring a context menu. The toolbar keyword maps to the toolbar state, in which the element is declaring a toolbar. The attribute may also be omitted. The missing value default is the list state, which indicates that the element is merely a list of commands that is neither declaring a context menu nor defining a toolbar.

If a menu element's type attribute is in the context menu state, then the element represents the commands of a context menu, and the user can only interact with the commands if that context menu is activated.

If a menu element's type attribute is in the toolbar state, then the element represents a list of active commands that the user can immediately interact with.

If a menu element's type attribute is in the list state, then the element either represents an unordered list of items (each represented by an li element), each of which represents a command that the user can perform or activate, or, if the element has no li element children, flow content describing available commands.

The label attribute gives the label of the menu. It is used by user agents to display nested menus in the UI. For example, a context menu containing another menu would use the nested menu's label attribute for the submenu's menu label.

The type and label IDL attributes must reflect the respective content attributes of the same name.

4.11.4.1 Introduction

Status: Last call for comments

This section is non-normative.

The menu element is used to define context menus and toolbars.

For example, the following represents a toolbar with three menu buttons on it, each of which has a dropdown menu with a series of options:

<menu type="toolbar">
 <li>
  <menu label="File">
   <button type="button" onclick="fnew()">New...</button>
   <button type="button" onclick="fopen()">Open...</button>
   <button type="button" onclick="fsave()">Save</button>
   <button type="button" onclick="fsaveas()">Save as...</button>
  </menu>
 </li>
 <li>
  <menu label="Edit">
   <button type="button" onclick="ecopy()">Copy</button>
   <button type="button" onclick="ecut()">Cut</button>
   <button type="button" onclick="epaste()">Paste</button>
  </menu>
 </li>
 <li>
  <menu label="Help">
   <li><a href="help.html">Help</a></li>
   <li><a href="about.html">About</a></li>
  </menu>
 </li>
</menu>

In a supporting user agent, this might look like this:

A toolbar with three buttons, labeled 'File', 'Edit', and 'Help'; where if you select the 'Edit' button you get a drop-down menu with three more options, 'Copy', 'Cut', and 'Paste'.

In a legacy user agent, the above would look like a bulleted list with three items, the first of which has four buttons, the second of which has three, and the third of which has two nested bullet points with two items consisting of links.

The following implements a similar toolbar, with a single button whose values, when selected, redirect the user to Web sites.

<form action="redirect.cgi">
 <menu type="toolbar">
  <label for="goto">Go to...</label>
  <menu label="Go">
   <select id="goto">
    <option value="" selected="selected"> Select site: </option>
    <option value="http://www.apple.com/"> Apple </option>
    <option value="http://www.mozilla.org/"> Mozilla </option>
    <option value="http://www.opera.com/"> Opera </option>
   </select>
   <span><input type="submit" value="Go"></span>
  </menu>
 </menu>
</form>

The behavior in supporting user agents is similar to the example above, but here the legacy behaviour consists of a single select element with a submit button. The submit button doesn't appear in the toolbar, because it is not a direct child of the menu element or of its li children.

4.11.4.2 Building menus and toolbars

Status: Last call for comments

A menu (or toolbar) consists of a list of zero or more of the following components:

Commands, which can be marked as default commands
Separators
Other menus (which allows the list to be nested)

The list corresponding to a particular menu element is built by iterating over its child nodes. For each child node in tree order, the required behavior depends on what the node is, as follows:

An element that defines a command: Append the command to the menu, respecting its facets.
An hr element
An option element that has a value attribute set to the empty string, and has a disabled attribute, and whose textContent consists of a string of one or more hyphens (U+002D HYPHEN-MINUS): Append a separator to the menu.
An li element
A label element: Iterate over the children of the element.
A menu element with no label attribute
A select element: Append a separator to the menu, then iterate over the children of the menu or select element, then append another separator.
A menu element with a label attribute
An optgroup element with a label attribute: Append a submenu to the menu, using the value of the element's label attribute as the label of the menu. The submenu must be constructed by taking the element and creating a new menu for it using the complete process described in this section.
Any other node: Ignore the node.

Once all the nodes have been processed as described above, the user agent must the post-process the menu as follows:

Except for separators, any menu item with no label, or whose label is the empty string, must be removed.
Any sequence of two or more separators in a row must be collapsed to a single separator.
Any separator at the start or end of the menu must be removed.

4.11.4.3 Context menus

Status: Last call for comments

The contextmenu attribute gives the element's context menu. The value must be the ID of a menu element in the DOM. If the node that would be obtained by the invoking the getElementById() method using the attribute's value as the only argument is null or not a menu element, then the element has no assigned context menu. Otherwise, the element's assigned context menu is the element so identified.

When an element's context menu is requested (e.g. by the user right-clicking the element, or pressing a context menu key), the UA must fire a simple event named contextmenu that bubbles and is cancelable at the element for which the menu was requested.

Typically, therefore, the firing of the contextmenu event will be the default action of a mouseup or keyup event. The exact sequence of events is UA-dependent, as it will vary based on platform conventions.

The default action of the contextmenu event depends on whether the element or one of its ancestors has a context menu assigned (using the contextmenu attribute) or not. If there is no context menu assigned, the default action must be for the user agent to show its default context menu, if it has one.

If the element or one of its ancestors does have a context menu assigned, then the user agent must fire a simple event named show at the menu element of the context menu of the nearest ancestor (including the element itself) with one assigned.

The default action of this event is that the user agent must show a context menu built from the menu element.

The user agent may also provide access to its default context menu, if any, with the context menu shown. For example, it could merge the menu items from the two menus together, or provide the page's context menu as a submenu of the default menu.

If the user dismisses the menu without making a selection, nothing in particular happens.

If the user selects a menu item that represents a command, then the UA must invoke that command's Action.

Context menus must not, while being shown, reflect changes in the DOM; they are constructed as the default action of the show event and must remain as constructed until dismissed.

User agents may provide means for bypassing the context menu processing model, ensuring that the user can always access the UA's default context menus. For example, the user agent could handle right-clicks that have the Shift key depressed in such a way that it does not fire the contextmenu event and instead always shows the default context menu.

The contextMenu attribute must reflect the contextmenu content attribute.

Here is an example of a context menu for an input control:

<form name="npc">
 <label>Character name: <input name=char type=text contextmenu=namemenu required></label>
 <menu type=context id=namemenu>
  <command label="Pick random name" onclick="document.forms.npc.elements.char.value = getRandomName()">
  <command label="Prefill other fields based on name" onclick="prefillFields(document.forms.npc.elements.char.value)">
 </menu>
</form>

This adds to items to the control's context menu, one called "Pick random name", and one called "Prefill other fields based on name". They invoke scripts that are not shown in the example above.

4.11.4.4 Toolbars

Status: Last call for comments

When a menu element has a type attribute in the toolbar state, then the user agent must build the menu for that menu element, and use the result in the rendering.

The user agent must reflect changes made to the menu's DOM, by immediately rebuilding the menu.

4.11.5 Commands

Status: Last call for comments

A command is the abstraction behind menu items, buttons, and links.

Type: The kind of command: "command", meaning it is a normal command; "radio", meaning that triggering the command will, amongst other things, set the Checked State to true (and probably uncheck some other commands); or "checkbox", meaning that triggering the command will, amongst other things, toggle the value of the Checked State.
ID: The name of the command, for referring to the command from the markup or from script. If a command has no ID, it is an anonymous command.
Label: The name of the command as seen by the user.
Hint: A helpful or descriptive string that can be shown to the user.
Icon: An absolute URL identifying a graphical image that represents the action. A command might not have an Icon.
Access Key: A key combination selected by the user agent that triggers the command. A command might not have an Access Key.
Hidden State: Whether the command is hidden or not (basically, whether it should be shown in menus).
Disabled State: Whether the command is relevant and can be triggered or not.
Checked State: Whether the command is checked or not.
Action: The actual effect that triggering the command will have. This could be a scripted event handler, a URL to which to navigate, or a form submission.

These facets are exposed on elements using the command API:

element . commandType: Exposes the Type facet of the command.
element . id: Exposes the ID facet of the command.
element . label: Exposes the Label facet of the command.
element . title: Exposes the Hint facet of the command.
element . icon: Exposes the Icon facet of the command.
element . accessKeyLabel: Exposes the Access Key facet of the command.
element . hidden: Exposes the Hidden State facet of the command.
element . disabled: Exposes the Disabled State facet of the command.
element . checked: Exposes the Checked State facet of the command.
element . click(): Triggers the Action of the command.

The commandType attribute must return a string whose value is either "command", "radio", or "checked", depending on whether the Type of the command defined by the element is "command", "radio", or "checked" respectively. If the element does not define a command, it must return null.

The label attribute must return the command's Label, or null if the element does not define a command or does not specify a Label. This attribute will be shadowed by the label IDL attribute on option and command elements.

The icon attribute must return the absolute URL of the command's Icon. If the element does not specify an icon, or if the element does not define a command, then the attribute must return null. This attribute will be shadowed by the icon IDL attribute on command elements.

The disabled attribute must return true if the command's Disabled State is that the command is disabled, and false if the command is not disabled. This attribute is not affected by the command's Hidden State. If the element does not define a command, the attribute must return false. This attribute will be shadowed by the disabled IDL attribute on button, input, option, and command elements.

The checked attribute must return true if the command's Checked State is that the command is checked, and false if it is that the command is not checked. If the element does not define a command, the attribute must return false. This attribute will be shadowed by the checked IDL attribute on input and command elements.

The ID facet is exposed by the id IDL attribute, the Hint facet is exposed by the title IDL attribute, the AccessKey facet is exposed by the accessKeyLabel IDL attribute, and the Hidden State facet is exposed by the hidden IDL attribute.

document . commands: Returns an HTMLCollection of the elements in the Document that define commands and have IDs.

The commands attribute of the document's HTMLDocument interface must return an HTMLCollection rooted at the Document node, whose filter matches only elements that define commands and have IDs.

User agents may expose the commands whose Hidden State facet is false (visible), e.g. in the user agent's menu bar. User agents are encouraged to do this especially for commands that have Access Keys, as a way to advertise those keys to the user.

4.11.5.1 Using the `a` element to define a command

Status: Last call for comments

An a element with an href attribute defines a command.

The Type of the command is "command".

The ID of the command is the value of the id attribute of the element, if the attribute is present and not empty. Otherwise the command is an anonymous command.

The Label of the command is the string given by the element's textContent IDL attribute.

The Hint of the command is the value of the title attribute of the element. If the attribute is not present, the Hint is the empty string.

The Icon of the command is the absolute URL obtained from resolving the value of the src attribute of the first img element descendant of the element, relative to that element, if there is such an element and resolving its attribute is successful. Otherwise, there is no Icon for the command.

The AccessKey of the command is the element's assigned access key, if any.

The Hidden State of the command is true (hidden) if the element has a hidden attribute, and false otherwise.

The Disabled State facet of the command is always false. (The command is always enabled.)

The Checked State of the command is always false. (The command is never checked.)

The Action of the command is to fire a click event at the element.

4.11.5.2 Using the `button` element to define a command

Status: Last call for comments

A button element always defines a command.

The Type, ID, Label, Hint, Icon, Access Key, Hidden State, Checked State, and Action facets of the command are determined as for a elements (see the previous section).

The Disabled State of the command mirrors the disabled state of the button.

4.11.5.3 Using the `input` element to define a command

Status: Last call for comments

An input element whose type attribute is in one of the Submit Button, Reset Button, Image Button, Button, Radio Button, or Checkbox states defines a command.

The Type of the command is "radio" if the type attribute is in the Radio Button state, "checkbox" if the type attribute is in the Checkbox state, and "command" otherwise.

The ID of the command is the value of the id attribute of the element, if the attribute is present and not empty. Otherwise the command is an anonymous command.

The Label of the command depends on the Type of the command:

If the Type is "command", then it is the string given by the value attribute, if any, and a UA-dependent, locale-dependent value that the UA uses to label the button itself if the attribute is absent.

Otherwise, the Type is "radio" or "checkbox". If the element is a labeled control, the textContent of the first label element in tree order whose labeled control is the element in question is the Label (in DOM terms, this is the string given by element.labels[0].textContent). Otherwise, the value of the value attribute, if present, is the Label. Otherwise, the Label is the empty string.

The Hint of the command is the value of the title attribute of the input element. If the attribute is not present, the Hint is the empty string.

If the element's type attribute is in the Image Button state, and the element has a src attribute, and that attribute's value can be successfully resolved relative to the element, then the Icon of the command is the absolute URL obtained from resolving that attribute that way. Otherwise, there is no Icon for the command.

The AccessKey of the command is the element's assigned access key, if any.

The Hidden State of the command is true (hidden) if the element has a hidden attribute, and false otherwise.

The Disabled State of the command mirrors the disabled state of the control.

The Checked State of the command is true if the command is of Type "radio" or "checkbox" and the element is checked attribute, and false otherwise.

The Action of the command, if the element has a defined activation behavior, is to run synthetic click activation steps on the element. Otherwise, it is just to fire a click event at the element.

4.11.5.4 Using the `option` element to define a command

Status: Last call for comments

An option element with an ancestor select element and either no value attribute or a value attribute that is not the empty string defines a command.

The Type of the command is "radio" if the option's nearest ancestor select element has no multiple attribute, and "checkbox" if it does.

The ID of the command is the value of the id attribute of the element, if the attribute is present and not empty. Otherwise the command is an anonymous command.

The Label of the command is the value of the option element's label attribute, if there is one, or the value of the option element's textContent IDL attribute if there isn't.

The Hint of the command is the string given by the element's title attribute, if any, and the empty string if the attribute is absent.

There is no Icon for the command.

The AccessKey of the command is the element's assigned access key, if any.

The Hidden State of the command is true (hidden) if the element has a hidden attribute, and false otherwise.

The Disabled State of the command is true (disabled) if the element is disabled or if its nearest ancestor select element is disabled, and false otherwise.

The Checked State of the command is true (checked) if the element's selectedness is true, and false otherwise.

The Action of the command depends on its Type. If the command is of Type "radio" then it must pick the option element. Otherwise, it must toggle the option element.

4.11.5.5 Using the `command` element to define a command

Status: Last call for comments

A command element defines a command.

The Type of the command is "radio" if the command's type attribute is "radio", "checkbox" if the attribute's value is "checkbox", and "command" otherwise.

The ID of the command is the value of the id attribute of the element, if the attribute is present and not empty. Otherwise the command is an anonymous command.

The Label of the command is the value of the element's label attribute, if there is one, or the empty string if it doesn't.

The Hint of the command is the string given by the element's title attribute, if any, and the empty string if the attribute is absent.

The Icon for the command is the absolute URL obtained from resolving the value of the element's icon attribute, relative to the element, if it has such an attribute and resolving it is successful. Otherwise, there is no Icon for the command.

The AccessKey of the command is the element's assigned access key, if any.

The Hidden State of the command is true (hidden) if the element has a hidden attribute, and false otherwise.

The Disabled State of the command is true (disabled) if the element has a disabled attribute, and false otherwise.

The Checked State of the command is true (checked) if the element has a checked attribute, and false otherwise.

The Action of the command, if the element has a defined activation behavior, is to run synthetic click activation steps on the element. Otherwise, it is just to fire a click event at the element.

4.11.5.6 Using the `accesskey` attribute on a `label` element to define a command

Status: Last call for comments

A label element that has an assigned access key and a labeled control and whose labeled control defines a command, itself defines a command.

The Type of the command is "command".

The ID of the command is the value of the id attribute of the element, if the attribute is present and not empty. Otherwise the command is an anonymous command.

The Label of the command is the string given by the element's textContent IDL attribute.

The Hint of the command is the value of the title attribute of the element.

There is no Icon for the command.

The AccessKey of the command is the element's assigned access key.

The Hidden State, Disabled State, and Action facets of the command are the same as the respective facets of the element's labeled control.

The Checked State of the command is always false. (The command is never checked.)

4.11.5.7 Using the `accesskey` attribute on a `legend` element to define a command

Status: Last call for comments

A legend element that has an assigned access key and is a child of a fieldset element that has a descendant that is not a descendant of the legend element and is neither a label element nor a legend element but that defines a command, itself defines a command.

The Type of the command is "command".

The ID of the command is the value of the id attribute of the element, if the attribute is present and not empty. Otherwise the command is an anonymous command.

The Label of the command is the string given by the element's textContent IDL attribute.

The Hint of the command is the value of the title attribute of the element.

There is no Icon for the command.

The AccessKey of the command is the element's assigned access key.

The Hidden State, Disabled State, and Action facets of the command are the same as the respective facets of the first element in tree order that is a descendant of the parent of the legend element that defines a command but is not a descendant of the legend element and is neither a label nor a legend element.

The Checked State of the command is always false. (The command is never checked.)

4.11.5.8 Using the `accesskey` attribute to define a command on other elements

Status: Last call for comments

An element that has an assigned access key defines a command.

If one of the other sections that define elements that define commands define that this element defines a command, then that section applies to this element, and this section does not. Otherwise, this section applies to that element.

The Type of the command is "command".

The ID of the command is the value of the id attribute of the element, if the attribute is present and not empty. Otherwise the command is an anonymous command.

The Label of the command depends on the element. If the element is a labeled control, the textContent of the first label element in tree order whose labeled control is the element in question is the Label (in DOM terms, this is the string given by element.labels[0].textContent). Otherwise, the Label is the textContent of the element itself.

The Hint of the command is the value of the title attribute of the element. If the attribute is not present, the Hint is the empty string.

There is no Icon for the command.

The AccessKey of the command is the element's assigned access key.

The Hidden State of the command is true (hidden) if the element has a hidden attribute, and false otherwise.

The Disabled State facet of the command is always false. (The command is always enabled.)

The Checked State of the command is always false. (The command is never checked.)

The Action of the command is to run the following steps:

If the element is focusable, run the focusing steps for the element.
If the element has a defined activation behavior, run synthetic click activation steps on the element.
Otherwise, if the element does not have a defined activation behavior, fire a click event at the element.

4.12 Links

Status: Last call for comments

4.12.1 Hyperlink elements

Status: Last call for comments

The a, area, and link elements can, in certain situations described in the definitions of those elements, represent hyperlinks.

The href attribute on a hyperlink element must have a value that is a valid URL. This URL is the destination resource of the hyperlink.

The href attribute on a and area elements is not required; when those elements do not have href attributes they do not represent hyperlinks.

The href attribute on the link element is required, but whether a link element represents a hyperlink or not depends on the value of the rel attribute of that element.

The target attribute, if present, must be a valid browsing context name or keyword. It gives the name of the browsing context that will be used. User agents use this name when following hyperlinks.

The ping attribute, if present, gives the URLs of the resources that are interested in being notified if the user follows the hyperlink. The value must be a set of space-separated tokens, each of which must be a valid URL. The value is used by the user agent for hyperlink auditing.

For a and area elements that represent hyperlinks, the relationship between the document containing the hyperlink and the destination resource indicated by the hyperlink is given by the value of the element's rel attribute, which must be a set of space-separated tokens. The allowed values and their meanings are defined below. The rel attribute has no default value. If the attribute is omitted or if none of the values in the attribute are recognized by the user agent, then the document has no particular relationship with the destination resource other than there being a hyperlink between the two.

The media attribute describes for which media the target document was designed. It is purely advisory. The value must be a valid media query. The default, if the media attribute is omitted, is "all".

The hreflang attribute on hyperlink elements, if present, gives the language of the linked resource. It is purely advisory. The value must be a valid BCP 47 language code. [BCP47] User agents must not consider this attribute authoritative — upon fetching the resource, user agents must use only language information associated with the resource to determine its language, not metadata included in the link to the resource.

The type attribute, if present, gives the MIME type of the linked resource. It is purely advisory. The value must be a valid MIME type. User agents must not consider the type attribute authoritative — upon fetching the resource, user agents must not use metadata included in the link to the resource to determine its type.

4.12.2 Following hyperlinks

Status: Last call for comments

When a user follows a hyperlink, the user agent must resolve the URL given by the href attribute of that hyperlink, relative to the hyperlink element, and if that is successful, must navigate a browsing context to the resulting absolute URL. In the case of server-side image maps, the URL of the hyperlink must further have its hyperlink suffix appended to it.

If resolving the URL fails, the user agent may report the error to the user in a user-agent-specific manner, may navigate to an error page to report the error, or may ignore the error and do nothing.

If the user indicated a specific browsing context when following the hyperlink, or if the user agent is configured to follow hyperlinks by navigating a particular browsing context, then that must be the browsing context that is navigated.

Otherwise, if the hyperlink element is an a or area element that has a target attribute, then the browsing context that is navigated must be chosen by applying the rules for choosing a browsing context given a browsing context name, using the value of the target attribute as the browsing context name. If these rules result in the creation of a new browsing context, it must be navigated with replacement enabled.

Otherwise, if the hyperlink element is a sidebar hyperlink and the user agent implements a feature that can be considered a secondary browsing context, such a secondary browsing context may be selected as the browsing context to be navigated.

Otherwise, if the hyperlink element is an a or area element with no target attribute, but one of the child nodes of the head element is a base element with a target attribute, then the browsing context that is navigated must be chosen by applying the rules for choosing a browsing context given a browsing context name, using the value of the target attribute of the first such base element as the browsing context name. If these rules result in the creation of a new browsing context, it must be navigated with replacement enabled.

Otherwise, the browsing context that must be navigated is the same browsing context as the one which the hyperlink element itself is in.

The navigation must be done with the browsing context that contains the Document object with which the hyperlink's element in question is associated as the source browsing context.

4.12.2.1 Hyperlink auditing

Status: Last call for comments. ISSUE-1 (PINGPOST) and ISSUE-2 (PINGUI) block progress to Last Call

If an a or area hyperlink element has a ping attribute, and the user follows the hyperlink, and the hyperlink's URL can be resolved, relative to the hyperlink element, without failure, then the user agent must take the ping attribute's value, split that string on spaces, resolve each resulting token relative to the hyperlink element, and then should send a request (as described below) to each of the resulting absolute URLs. (Tokens that fail to resolve are ignored.) This may be done in parallel with the primary request, and is independent of the result of that request.

User agents should allow the user to adjust this behavior, for example in conjunction with a setting that disables the sending of HTTP Referer (sic) headers. Based on the user's preferences, UAs may either ignore the ping attribute altogether, or selectively ignore URLs in the list (e.g. ignoring any third-party URLs).

For URLs that are HTTP URLs, the requests must be performed by fetching the specified URLs using the POST method, with an entity body with the MIME type text/ping consisting of the four-character string "PING", from the origin of the Document containing the hyperlink. All relevant cookie and HTTP authentication headers must be included in the request. Which other headers are required depends on the URLs involved.

If both the address of the Document object containing the hyperlink being audited and the ping URL have the same origin: The request must include a Ping-From HTTP header with, as its value, the address of the document containing the hyperlink, and a Ping-To HTTP header with, as its value, the address of the absolute URL of the target of the hyperlink. The request must not include a Referer (sic) HTTP header.
Otherwise, if the origins are different, but the document containing the hyperlink being audited was not retrieved over an encrypted connection: The request must include a Referer (sic) HTTP header with, as its value, the current address of the document containing the hyperlink, a Ping-From HTTP header with the same value, and a Ping-To HTTP header with, as its value, the address of the target of the hyperlink.
Otherwise, the origins are different and the document containing the hyperlink being audited was retrieved over an encrypted connection: The request must include a Ping-To HTTP header with, as its value, the address of the target of the hyperlink. The request must neither include a Referer (sic) HTTP header nor include a Ping-From HTTP header.

To save bandwidth, implementors might also wish to consider omitting optional headers such as Accept from these requests.

User agents must, unless otherwise specified by the user, honor the HTTP headers (including, in particular, redirects and HTTP cookie headers), but must ignore any entity bodies returned in the responses. User agents may close the connection prematurely once they start receiving an entity body. [COOKIES]

For URLs that are not HTTP URLs, the requests must be performed by fetching the specified URL normally, and discarding the results.

When the ping attribute is present, user agents should clearly indicate to the user that following the hyperlink will also cause secondary requests to be sent in the background, possibly including listing the actual target URLs.

For example, a visual user agent could include the hostnames of the target ping URLs along with the hyperlink's actual URL in a status bar or tooltip.

The ping attribute is redundant with pre-existing technologies like HTTP redirects and JavaScript in allowing Web pages to track which off-site links are most popular or allowing advertisers to track click-through rates.

However, the ping attribute provides these advantages to the user over those alternatives:

It allows the user to see the final target URL unobscured.
It allows the UA to inform the user about the out-of-band notifications.
It allows the user to disable the notifications without losing the underlying link functionality.
It allows the UA to optimize the use of available network bandwidth so that the target page loads faster.

Thus, while it is possible to track users without this feature, authors are encouraged to use the ping attribute so that the user agent can make the user experience more transparent.

4.12.3 Link types

Status: Last call for comments

The following table summarizes the link types that are defined by this specification. This table is non-normative; the actual definitions for the link types are given in the next few sections.

In this section, the term referenced document refers to the resource identified by the element representing the link, and the term current document refers to the resource within which the element representing the link finds itself.

To determine which link types apply to a link, a, or area element, the element's rel attribute must be split on spaces. The resulting tokens are the link types that apply to that element.

Except where otherwise specified, a keyword must not be specified more than once per rel attribute.

The link types that contain no U+003A COLON characters (:), including all those defined in this specification, are ASCII case-insensitive values, and must be compared as such.

Thus, rel="next" is the same as rel="NEXT".

Link type	Effect on...		Brief description
Link type	`link`	`a` and `area`	Brief description
`alternate`	Hyperlink	Hyperlink	Gives alternate representations of the current document.
`archives`	Hyperlink	Hyperlink	Provides a link to a collection of records, documents, or other materials of historical interest.
`author`	Hyperlink	Hyperlink	Gives a link to the current document's author.
`bookmark`	not allowed	Hyperlink	Gives the permalink for the nearest ancestor section.
`external`	not allowed	Hyperlink	Indicates that the referenced document is not part of the same site as the current document.
`first`	Hyperlink	Hyperlink	Indicates that the current document is a part of a series, and that the first document in the series is the referenced document.
`help`	Hyperlink	Hyperlink	Provides a link to context-sensitive help.
`icon`	External Resource	not allowed	Imports an icon to represent the current document.
`index`	Hyperlink	Hyperlink	Gives a link to the document that provides a table of contents or index listing the current document.
`last`	Hyperlink	Hyperlink	Indicates that the current document is a part of a series, and that the last document in the series is the referenced document.
`license`	Hyperlink	Hyperlink	Indicates that the main content of the current document is covered by the copyright license described by the referenced document.
`next`	Hyperlink	Hyperlink	Indicates that the current document is a part of a series, and that the next document in the series is the referenced document.
`nofollow`	not allowed	Hyperlink	Indicates that the current document's original author or publisher does not endorse the referenced document.
`noreferrer`	not allowed	Hyperlink	Requires that the user agent not send an HTTP `Referer` (sic) header if the user follows the hyperlink.
`pingback`	External Resource	not allowed	Gives the address of the pingback server that handles pingbacks to the current document.
`prefetch`	External Resource	not allowed	Specifies that the target resource should be preemptively cached.
`prev`	Hyperlink	Hyperlink	Indicates that the current document is a part of a series, and that the previous document in the series is the referenced document.
`search`	Hyperlink	Hyperlink	Gives a link to a resource that can be used to search through the current document and its related pages.
`stylesheet`	External Resource	not allowed	Imports a stylesheet.
`sidebar`	Hyperlink	Hyperlink	Specifies that the referenced document, if retrieved, is intended to be shown in the browser's sidebar (if it has one).
`tag`	Hyperlink	Hyperlink	Gives a tag (identified by the given address) that applies to the current document.
`up`	Hyperlink	Hyperlink	Provides a link to a document giving the context for the current document.

Some of the types described below list synonyms for these values. These are to be handled as specified by user agents, but must not be used in documents.

4.12.3.1 Link type "`alternate`"

Status: Last call for comments

The alternate keyword may be used with link, a, and area elements. For link elements, if the rel attribute does not also contain the keyword stylesheet, it creates a hyperlink; but if it does also contain the keyword stylesheet, the alternate keyword instead modifies the meaning of the stylesheet keyword in the way described for that keyword, and the rest of this subsection doesn't apply.

The alternate keyword indicates that the referenced document is an alternate representation of the current document.

The nature of the referenced document is given by the media, hreflang, and type attributes.

If the alternate keyword is used with the media attribute, it indicates that the referenced document is intended for use with the media specified.

If the alternate keyword is used with the hreflang attribute, and that attribute's value differs from the root element's language, it indicates that the referenced document is a translation.

If the alternate keyword is used with the type attribute, it indicates that the referenced document is a reformulation of the current document in the specified format.

The media, hreflang, and type attributes can be combined when specified with the alternate keyword.

For example, the following link is a French translation that uses the PDF format:

<link rel=alternate type=application/pdf hreflang=fr href=manual-fr>

If the alternate keyword is used with the type attribute set to the value application/rss+xml or the value application/atom+xml, then it indicates that the referenced document is a syndication feed (though not necessarily syndicating exactly the same content as the current page).

The first link, a, or area element in the document (in tree order) with the alternate keyword used with the type attribute set to the value application/rss+xml or the value application/atom+xml must be treated as the default syndication feed for the purposes of feed autodiscovery.

The following link element gives the syndication feed for the current page:

<link rel="alternate" type="application/atom+xml" href="data.xml">

The following extract offers various different syndication feeds:

<p>You can access the planets database using Atom feeds:</p>
<ul>
 <li><a href="recently-visited-planets.xml" rel="alternate" type="application/atom+xml">Recently Visited Planets</a></li>
 <li><a href="known-bad-planets.xml" rel="alternate" type="application/atom+xml">Known Bad Planets</a></li>
 <li><a href="unexplored-planets.xml" rel="alternate" type="application/atom+xml">Unexplored Planets</a></li>
</ul>

The alternate link relationship is transitive — that is, if a document links to two other documents with the link type "alternate", then, in addition to implying that those documents are alternative representations of the first document, it is also implying that those two documents are alternative representations of each other.

4.12.3.2 Link type "`archives`"

Status: Last call for comments

The archives keyword may be used with link, a, and area elements. For link elements, it creates a hyperlink.

The archives keyword indicates that the referenced document describes a collection of records, documents, or other materials of historical interest.

A blog's index page could link to an index of the blog's past posts with rel="archives".

Synonyms: For historical reasons, user agents must also treat the keyword "archive" like the archives keyword.

4.12.3.3 Link type "`author`"

Status: Last call for comments

The author keyword may be used with link, a, and area elements. For link elements, it creates a hyperlink.

For a and area elements, the author keyword indicates that the referenced document provides further information about the author of the nearest article element ancestor of the element defining the hyperlink, if there is one, or of the page as a whole, otherwise.

For link elements, the author keyword indicates that the referenced document provides further information about the author for the page as a whole.

The "referenced document" can be, and often is, a mailto: URL giving the e-mail address of the author. [MAILTO]

Synonyms: For historical reasons, user agents must also treat link, a, and area elements that have a rev attribute with the value "made" as having the author keyword specified as a link relationship.

4.12.3.4 Link type "`bookmark`"

Status: Last call for comments

The bookmark keyword may be used with a and area elements.

The bookmark keyword gives a permalink for the nearest ancestor article element of the linking element in question, or of the section the linking element is most closely associated with, if there are no ancestor article elements.

The following snippet has three permalinks. A user agent could determine which permalink applies to which part of the spec by looking at where the permalinks are given.

 ...
 <body>
  <h1>Example of permalinks</h1>
  <div id="a">
   <h2>First example</h2>
   <p><a href="a.html" rel="bookmark">This</a> permalink applies to
   only the content from the first H2 to the second H2. The DIV isn't
   exactly that section, but it roughly corresponds to it.</p>
  </div>
  <h2>Second example</h2>
  <article id="b">
   <p><a href="b.html" rel="bookmark">This</a> permalink applies to
   the outer ARTICLE element (which could be, e.g., a blog post).</p>
   <article id="c">
    <p><a href="c.html" rel="bookmark">This</a> permalink applies to
    the inner ARTICLE element (which could be, e.g., a blog comment).</p>
   </article>
  </article>
 </body>
 ...

4.12.3.5 Link type "`external`"

Status: Last call for comments

The external keyword may be used with a and area elements.

The external keyword indicates that the link is leading to a document that is not part of the site that the current document forms a part of.

4.12.3.6 Link type "`help`"

Status: Last call for comments

The help keyword may be used with link, a, and area elements. For link elements, it creates a hyperlink.

For a and area elements, the help keyword indicates that the referenced document provides further help information for the parent of the element defining the hyperlink, and its children.

In the following example, the form control has associated context-sensitive help. The user agent could use this information, for example, displaying the referenced document if the user presses the "Help" or "F1" key.

 <p><label> Topic: <input name=topic> <a href="help/topic.html" rel="help">(Help)</a></label></p>

For link elements, the help keyword indicates that the referenced document provides help for the page as a whole.

4.12.3.7 Link type "`icon`"

Status: Last call for comments

The icon keyword may be used with link elements, for which it creates an external resource link.

The specified resource is an icon representing the page or site, and should be used by the user agent when representing the page in the user interface.

Icons could be auditory icons, visual icons, or other kinds of icons. If multiple icons are provided, the user agent must select the most appropriate icon according to the type, media, and sizes attributes. If there are multiple equally appropriate icons, user agents must use the last one declared in tree order. If the user agent tries to use an icon but that icon is determined, upon closer examination, to in fact be inappropriate (e.g. because it uses an unsupported format), then the user agent must try the next-most-appropriate icon as determined by the attributes.

There is no default type for resources given by the icon keyword. However, for the purposes of determining the type of the resource, user agents must expect the resource to be an image.

The sizes attribute gives the sizes of icons for visual media.

If specified, the attribute must have a value that is an unordered set of unique space-separated tokens. The values must all be either any or a value that consists of two valid non-negative integers that do not have a leading U+0030 DIGIT ZERO (0) character and that are separated by a single U+0078 LATIN SMALL LETTER X character (x).

The keywords represent icon sizes.

To parse and process the attribute's value, the user agent must first split the attribute's value on spaces, and must then parse each resulting keyword to determine what it represents.

The any keyword represents that the resource contains a scalable icon, e.g. as provided by an SVG image.

Other keywords must be further parsed as follows to determine what they represent:

If the keyword doesn't contain exactly one U+0078 LATIN SMALL LETTER X character (x), then this keyword doesn't represent anything. Abort these steps for that keyword.
Let width string be the string before the "x".
Let height string be the string after the "x".
If either width string or height string start with a U+0030 DIGIT ZERO (0) character or contain any characters other than characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), then this keyword doesn't represent anything. Abort these steps for that keyword.
Apply the rules for parsing non-negative integers to width string to obtain width.
Apply the rules for parsing non-negative integers to height string to obtain height.
The keyword represents that the resource contains a bitmap icon with a width of width device pixels and a height of height device pixels.

The keywords specified on the sizes attribute must not represent icon sizes that are not actually available in the linked resource.

If the attribute is not specified, then the user agent must assume that the given icon is appropriate, but less appropriate than an icon of a known and appropriate size.

The following snippet shows the top part of an application with several icons.

<!DOCTYPE HTML>
<html>
 <head>
  <title>lsForums — Inbox</title>
  <link rel=icon href=favicon.png sizes="16x16" type="image/png">
  <link rel=icon href=windows.ico sizes="32x32 48x48" type="image/vnd.microsoft.icon">
  <link rel=icon href=mac.icns sizes="128x128 512x512 8192x8192 32768x32768">
  <link rel=icon href=iphone.png sizes="59x60" type="image/png">
  <link rel=icon href=gnome.svg sizes="any" type="image/svg+xml">
  <link rel=stylesheet href=lsforums.css>
  <script src=lsforums.js></script>
  <meta name=application-name content="lsForums">
 </head>
 <body>
  ...

4.12.3.8 Link type "`license`"

Status: Last call for comments

The license keyword may be used with link, a, and area elements. For link elements, it creates a hyperlink.

The license keyword indicates that the referenced document provides the copyright license terms under which the main content of the current document is provided.

This specification does not specify how to distinguish between the main content of a document and content that is not deemed to be part of that main content. The distinction should be made clear to the user.

Consider a photo sharing site. A page on that site might describe and show a photograph, and the page might be marked up as follows:

<!DOCTYPE HTML>
<html>
 <head>
  <title>Exampl Pictures: Kissat</title>
  <link rel="stylesheet" href="/style/default">
 </head>
 <body>
  <h1>Kissat</h1>
  <nav>
   <a href="../">Return to photo index</a>
  </nav>
  <figure>
   <img src="/pix/39627052_fd8dcd98b5.jpg">
   <figcaption>Kissat</figcaption>
  </figure>
  <p>One of them has six toes!</p>
  <p><small><a rel="license" href="http://www.opensource.org/licenses/mit-license.php">MIT Licensed</a></small></p>
  <footer>
   <a href="/">Home</a> | <a href="../">Photo index</a>
   <p><small>© copyright 2009 Exampl Pictures. All Rights Reserved.</small></p>
  </footer>
 </body>
</html>

In this case the license applies to just the photo (the main content of the document), not the whole document. In particular not the design of the page itself, which is covered by the copyright given at the bottom of the document. This could be made clearer in the styling (e.g. making the license link prominently positioned near the photograph, while having the page copyright in light small text at the foot of the page.

Synonyms: For historical reasons, user agents must also treat the keyword "copyright" like the license keyword.

4.12.3.9 Link type "`nofollow`"

Status: Last call for comments

The nofollow keyword may be used with a and area elements.

The nofollow keyword indicates that the link is not endorsed by the original author or publisher of the page, or that the link to the referenced document was included primarily because of a commercial relationship between people affiliated with the two pages.

4.12.3.10 Link type "`noreferrer`"

Status: Last call for comments

The noreferrer keyword may be used with a and area elements.

It indicates that no referrer information is to be leaked when following the link.

If a user agent follows a link defined by an a or area element that has the noreferrer keyword, the user agent must not include a Referer (sic) HTTP header (or equivalent for other protocols) in the request.

This keyword also causes the opener attribute to remain null if the hyperlink creates a new browsing context.

4.12.3.11 Link type "`pingback`"

Status: Last call for comments

The pingback keyword may be used with link elements, for which it creates an external resource link.

For the semantics of the pingback keyword, see the Pingback 1.0 specification. [PINGBACK]

4.12.3.12 Link type "`prefetch`"

Status: Last call for comments

The prefetch keyword may be used with link elements, for which it creates an external resource link.

The prefetch keyword indicates that preemptively fetching and caching the specified resource is likely to be beneficial, as it is highly likely that the user will require this resource.

There is no default type for resources given by the prefetch keyword.

4.12.3.13 Link type "`search`"

Status: Last call for comments

The search keyword may be used with link, a, and area elements. For link elements, it creates a hyperlink.

The search keyword indicates that the referenced document provides an interface specifically for searching the document and its related resources.

OpenSearch description documents can be used with link elements and the search link type to enable user agents to autodiscover search interfaces. [OPENSEARCH]

4.12.3.14 Link type "`stylesheet`"

Status: Last call for comments

The stylesheet keyword may be used with link elements, for which it creates an external resource link that contributes to the styling processing model.

The specified resource is a resource that describes how to present the document. Exactly how the resource is to be processed depends on the actual type of the resource.

If the alternate keyword is also specified on the link element, then the link is an alternative stylesheet; in this case, the title attribute must be specified on the link element, with a non-empty value.

The default type for resources given by the stylesheet keyword is text/css.

Quirk: If the document has been set to quirks mode and the Content-Type metadata of the external resource is not a supported style sheet type, the user agent must instead assume it to be text/css.

4.12.3.15 Link type "`sidebar`"

Status: Last call for comments

The sidebar keyword may be used with link, a, and area elements. For link elements, it creates a hyperlink.

The sidebar keyword indicates that the referenced document, if retrieved, is intended to be shown in a secondary browsing context (if possible), instead of in the current browsing context.

A hyperlink element with the sidebar keyword specified is a sidebar hyperlink.

4.12.3.16 Link type "`tag`"

Status: Last call for comments

The tag keyword may be used with link, a, and area elements. For link elements, it creates a hyperlink.

The tag keyword indicates that the tag that the referenced document represents applies to the current document.

Since it indicates that the tag applies to the current document, it would be inappropriate to use this keyword in the markup of a tag cloud, which lists the popular tag across a set of pages.

4.12.3.17 Hierarchical link types

Status: Last call for comments

Some documents form part of a hierarchical structure of documents.

A hierarchical structure of documents is one where each document can have various subdocuments. The document of which a document is a subdocument is said to be the document's parent. A document with no parent forms the top of the hierarchy.

A document may be part of multiple hierarchies.

4.12.3.17.1 Link type "`index`"

Status: Last call for comments

The index keyword may be used with link, a, and area elements. For link elements, it creates a hyperlink.

The index keyword indicates that the document is part of a hierarchical structure, and that the link is leading to the document that is the top of the hierarchy. It conveys more information when used with the up keyword (q.v.).

Synonyms: For historical reasons, user agents must also treat the keywords "top", "contents", and "toc" like the index keyword.

4.12.3.17.2 Link type "`up`"

Status: Last call for comments

The up keyword may be used with link, a, and area elements. For link elements, it creates a hyperlink.

The up keyword indicates that the document is part of a hierarchical structure, and that the link is leading to a document that is an ancestor of the current document.

The up keyword may be repeated within a rel attribute to indicate the hierarchical distance from the current document to the referenced document. If it occurs only once, then the link is leading to the current document's parent; each additional occurrence of the keyword represents one further level. If the index keyword is also present, then the number of up keywords is the depth of the current page relative to the top of the hierarchy. Only one link is created for the set of one or more up keywords and, if present, the index keyword.

If the page is part of multiple hierarchies, then they should be described in different paragraphs. User agents must scope any interpretation of the up and index keywords together indicating the depth of the hierarchy to the paragraph in which the link finds itself, if any, or to the document otherwise.

When two links have both the up and index keywords specified together in the same scope and contradict each other by having a different number of up keywords, the link with the greater number of up keywords must be taken as giving the depth of the document.

This can be used to mark up a navigation style sometimes known as bread crumbs. In the following example, the current page can be reached via two paths.

<nav>
 <p>
  <a href="/" rel="index up up up">Main</a> >
  <a href="/products/" rel="up up">Products</a> >
  <a href="/products/dishwashers/" rel="up">Dishwashers</a> >
  <a>Second hand</a>
 </p>
 <p>
  <a href="/" rel="index up up">Main</a> >
  <a href="/second-hand/" rel="up">Second hand</a> >
  <a>Dishwashers</a>
 </p>
</nav>

The relList IDL attribute (e.g. on the a element) does not currently represent multiple up keywords (the interface hides duplicates).

4.12.3.18 Sequential link types

Status: Last call for comments

Some documents form part of a sequence of documents.

A sequence of documents is one where each document can have a previous sibling and a next sibling. A document with no previous sibling is the start of its sequence, a document with no next sibling is the end of its sequence.

A document may be part of multiple sequences.

4.12.3.18.1 Link type "`first`"

Status: Last call for comments

The first keyword may be used with link, a, and area elements. For link elements, it creates a hyperlink.

The first keyword indicates that the document is part of a sequence, and that the link is leading to the document that is the first logical document in the sequence.

Synonyms: For historical reasons, user agents must also treat the keywords "begin" and "start" like the first keyword.

4.12.3.18.2 Link type "`last`"

Status: Last call for comments

The last keyword may be used with link, a, and area elements. For link elements, it creates a hyperlink.

The last keyword indicates that the document is part of a sequence, and that the link is leading to the document that is the last logical document in the sequence.

Synonyms: For historical reasons, user agents must also treat the keyword "end" like the last keyword.

4.12.3.18.3 Link type "`next`"

Status: Last call for comments

The next keyword may be used with link, a, and area elements. For link elements, it creates a hyperlink.

The next keyword indicates that the document is part of a sequence, and that the link is leading to the document that is the next logical document in the sequence.

4.12.3.18.4 Link type "`prev`"

Status: Last call for comments

The prev keyword may be used with link, a, and area elements. For link elements, it creates a hyperlink.

The prev keyword indicates that the document is part of a sequence, and that the link is leading to the document that is the previous logical document in the sequence.

Synonyms: For historical reasons, user agents must also treat the keyword "previous" like the prev keyword.

4.12.3.19 Other link types

Status: Last call for comments

Extensions to the predefined set of link types may be registered in the WHATWG Wiki RelExtensions page. [WHATWGWIKI]

Anyone is free to edit the WHATWG Wiki RelExtensions page at any time to add a type. Extension types must be specified with the following information:

Keyword

The actual value being defined. The value should not be confusingly similar to any other defined value (e.g. differing only in case).

If the value contains a U+003A COLON character (:), it must also be an absolute URL.

Effect on... link

One of the following:

not allowed: The keyword is not allowed to be specified on link elements.
Hyperlink: The keyword may be specified on a link element; it creates a hyperlink link.
External Resource: The keyword may be specified on a link element; it creates a external resource link.

Effect on... a and area

One of the following:

not allowed: The keyword is not allowed to be specified on a and area elements.
Hyperlink: The keyword may be specified on a and area elements.

Brief description

A short non-normative description of what the keyword's meaning is.

Specification

A link to a more detailed description of the keyword's semantics and requirements. It could be another page on the Wiki, or a link to an external page.

Synonyms

A list of other keyword values that have exactly the same processing requirements. Authors should not use the values defined to be synonyms, they are only intended to allow user agents to support legacy content. Anyone may remove synonyms that are not used in practice; only names that need to be processed as synonyms for compatibility with legacy content are to be registered in this way.

Status

One of the following:

Proposed: The keyword has not received wide peer review and approval. Someone has proposed it and is, or soon will be, using it.
Ratified: The keyword has received wide peer review and approval. It has a specification that unambiguously defines how to handle pages that use the keyword, including when they use it in incorrect ways.
Discontinued: The keyword has received wide peer review and it has been found wanting. Existing pages are using this keyword, but new pages should avoid it. The "brief description" and "specification" entries will give details of what authors should use instead, if anything.

If a keyword is found to be redundant with existing values, it should be removed and listed as a synonym for the existing value.

If a keyword is registered in the "proposed" state for a period of a month or more without being used or specified, then it may be removed from the registry.

If a keyword is added with the "proposed" status and found to be redundant with existing values, it should be removed and listed as a synonym for the existing value. If a keyword is added with the "proposed" status and found to be harmful, then it should be changed to "discontinued" status.

Anyone can change the status at any time, but should only do so in accordance with the definitions above.

Conformance checkers must use the information given on the WHATWG Wiki RelExtensions page to establish if a value is allowed or not: values defined in this specification or marked as "proposed" or "ratified" must be accepted when used on the elements for which they apply as described in the "Effect on..." field, whereas values marked as "discontinued" or not listed in either this specification or on the aforementioned page must be rejected as invalid. Conformance checkers may cache this information (e.g. for performance reasons or to avoid the use of unreliable network connectivity).

When an author uses a new type not defined by either this specification or the Wiki page, conformance checkers should offer to add the value to the Wiki, with the details described above, with the "proposed" status.

Types defined as extensions in the WHATWG Wiki RelExtensions page with the status "proposed" or "ratified" may be used with the rel attribute on link, a, and area elements in accordance to the "Effect on..." field. [WHATWGWIKI]

4.13 Common idioms without dedicated elements

Status: Last call for comments. ISSUE-89 (idioms) blocks progress to Last Call

4.13.1 Tag clouds

Status: Last call for comments

This specification does not define any markup specifically for marking up lists of keywords that apply to a group of pages (also known as tag clouds). In general, authors are encouraged to either mark up such lists using ul elements with explicit inline counts that are then hidden and turned into a presentational effect using a style sheet, or to use SVG.

Here, three tags are included in a short tag cloud:

<style>
@media screen, print, handheld, tv {
  /* should be ignored by non-visual browsers */
  .tag-cloud > li > span { display: none; }
  .tag-cloud > li { display: inline; }
  .tag-cloud-1 { font-size: 0.7em; }
  .tag-cloud-2 { font-size: 0.9em; }
  .tag-cloud-3 { font-size: 1.1em; }
  .tag-cloud-4 { font-size: 1.3em; }
  .tag-cloud-5 { font-size: 1.5em; }
}
</style>
...
<ul class="tag-cloud">
 <li class="tag-cloud-4"><a title="28 instances" href="/t/apple">apple</a> <span>(popular)</span>
 <li class="tag-cloud-2"><a title="6 instances"  href="/t/kiwi">kiwi</a> <span>(rare)</span>
 <li class="tag-cloud-5"><a title="41 instances" href="/t/pear">pear</a> <span>(very popular)</span>
</ul>

The actual frequency of each tag is given using the title attribute. A CSS style sheet is provided to convert the markup into a cloud of differently-sized words, but for user agents that do not support CSS or are not visual, the markup contains annotations like "(popular)" or "(rare)" to categorize the various tags by frequency, thus enabling all users to benefit from the information.

The ul element is used (rather than ol) because the order is not particularly important: while the list is in fact ordered alphabetically, it would convey the same information if ordered by, say, the length of the tag.

The tag rel-keyword is not used on these a elements because they do not represent tags that apply to the page itself; they are just part of an index listing the tags themselves.

4.13.2 Conversations

Status: Last call for comments

This specification does not define a specific element for marking up conversations, meeting minutes, chat transcripts, dialogues in screenplays, instant message logs, and other situations where different players take turns in discourse.

Instead, authors are encouraged to mark up conversations using p elements and punctuation. Authors who need to mark the speaker for styling purposes are encouraged to use span or b. Paragraphs with their text wrapped in the i element can be used for marking up stage directions.

This example demonstrates this using an extract from Abbot and Costello's famous sketch, Who's on first:

<p> Costello: Look, you gotta first baseman?
<p> Abbott: Certainly.
<p> Costello: Who's playing first?
<p> Abbott: That's right.
<p> Costello becomes exasperated.
<p> Costello: When you pay off the first baseman every month, who gets the money?
<p> Abbott: Every dollar of it.

The following extract shows how an IM conversation log could be marked up.

<p> <time>14:22</time> <b>egof</b> I'm not that nerdy, I've only seen 30% of the star trek episodes
<p> <time>14:23</time> <b>kaj</b> if you know what percentage of the star trek episodes you have seen, you are inarguably nerdy
<p> <time>14:23</time> <b>egof</b> it's unarguably
<p> <time>14:23</time> <i>* kaj blinks</i>
<p> <time>14:24</time> <b>kaj</b> you are not helping your case

4.13.3 Footnotes

Status: Last call for comments

HTML does not have a dedicated mechanism for marking up footnotes. Here are the recommended alternatives.

For short inline annotations, the title attribute should be used.

In this example, two parts of a dialogue are annotated with footnote-like content using the title attribute.

<p> <b>Customer</b>: Hello! I wish to register a complaint. Hello. Miss?
<p> <b>Shopkeeper</b>: <span title="Colloquial pronunciation of 'What do you'"
>Watcha</span> mean, miss?
<p> <b>Customer</b>: Uh, I'm sorry, I have a cold. I wish to make a complaint.
<p> <b>Shopkeeper</b>: Sorry, <span title="This is, of course, a lie.">we're
closing for lunch</span>.

For longer annotations, the a element should be used, pointing to an element later in the document. The convention is that the contents of the link be a number in square brackets.

In this example, a footnote in the dialogue links to a paragraph below the dialogue. The paragraph then reciprocally links back to the dialogue, allowing the user to return to the location of the footnote.

<p> Announcer: Number 16: The <i>hand</i>.
<p> Interviewer: Good evening. I have with me in the studio tonight
Mr Norman St John Polevaulter, who for the past few years has been
contradicting people. Mr Polevaulter, why <em>do</em> you
contradict people?
<p> Norman: I don't. <sup><a href="#fn1" id="r1">[1]</a></sup>
<p> Interviewer: You told me you did!
...
<section>
 <p id="fn1"><a href="#r1">[1]</a> This is, naturally, a lie,
 but paradoxically if it were true he could not say so without
 contradicting the interviewer and thus making it false.</p>
</section>

For side notes, longer annotations that apply to entire sections of the text rather than just specific words or sentences, the aside element should be used.

In this example, a sidebar is given after a dialogue, giving it some context.

<p> <span class="speaker">Customer</span>: I will not buy this record, it is scratched.
<p> <span class="speaker">Shopkeeper</span>: I'm sorry?
<p> <span class="speaker">Customer</span>: I will not buy this record, it is scratched.
<p> <span class="speaker">Shopkeeper</span>: No no no, this's'a tobacconist's.
<aside>
 <p>In 1970, the British Empire lay in ruins, and foreign
 nationalists frequented the streets — many of them Hungarians
 (not the streets — the foreign nationals). Sadly, Alexander
 Yalt has been publishing incompetently-written phrase books.
</aside>

For figures or tables, footnotes can be included in the relevant figcaption or caption element, or in surrounding prose.

In this example, a table has cells with footnotes that are given in prose. A figure element is used to give a single legend to the combination of the table and its footnotes.

<figure>
 <figcaption>Table 1. Alternative activities for knights.</figcaption>
 <table>
  <tr>
   <th> Activity
   <th> Location
   <th> Cost
  <tr>
   <td> Dance
   <td> Wherever possible
   <td> £0<sup><a href="#fn1">1</a></sup>
  <tr>
   <td> Routines, chorus scenes<sup><a href="#fn2">2</a></sup>
   <td> Undisclosed
   <td> Undisclosed
  <tr>
   <td> Dining<sup><a href="#fn3">3</a></sup>
   <td> Camelot
   <td> Cost of ham, jam, and spam<sup><a href="#fn4">4</a></sup>
 </table>
 <p id="fn1">1. Assumed.</p>
 <p id="fn2">2. Footwork impeccable.</p>
 <p id="fn3">3. Quality described as "well".</p>
 <p id="fn4">4. A lot.</p>
</figure>

4.14 Matching HTML elements using selectors

Status: Last call for comments

4.14.1 Case-sensitivity

Status: Last call for comments

Attribute and element names of HTML elements in HTML documents must be treated as ASCII case-insensitive.

Classes from the class attribute of HTML elements in documents that are in quirks mode must be treated as ASCII case-insensitive.

Attribute selectors on an HTML element in an HTML document must treat the values of attributes with the following names as ASCII case-insensitive:

accept
accept-charset
align
alink
axis
bgcolor
charset
checked
clear
codetype
color
compact
declare
defer
dir
direction
disabled
enctype
face
frame
hreflang
http-equiv
lang
language
link
media
method
multiple
nohref
noresize
noshade
nowrap
readonly
rel
rev
rules
scope
scrolling
selected
shape
target
text
type
valign
valuetype
vlink

All other attribute values on HTML elements must be treated as case-sensitive.

4.14.2 Pseudo-classes

There are a number of dynamic selectors that can be used with HTML. This section defines when these selectors match HTML elements.

:link

:visited

All a elements that have an href attribute, all area elements that have an href attribute, and all link elements that have an href attribute, must match one of :link and :visited.

:active

The :active pseudo-class must match the following elements between the time the user begins to activate the element and the time the user stops activating the element:

a elements that have an href attribute
area elements that have an href attribute
link elements that have an href attribute
button elements that are not disabled
input elements whose type attribute is in the Submit Button, Image Button, Reset Button, or Button state
command elements that do not have a disabled attribute
any other element, if it is specially focusable

For example, if the user is using a keyboard to push a button element by pressing the space bar, the element would match this pseudo-class in between the time that the element received the keydown event and the time the element received the keyup event.

:enabled

The :enabled pseudo-class must match the following elements:

a elements that have an href attribute
area elements that have an href attribute
link elements that have an href attribute
button elements that are not disabled
input elements whose type attribute are not in the Hidden state and that are not disabled
select elements that are not disabled
textarea elements that are not disabled
option elements that do not have a disabled attribute
command elements that do not have a disabled attribute
li elements that are children of menu elements, and that have a child element that defines a command, if the first such element's Disabled State facet is false (not disabled)

:disabled

The :disabled pseudo-class must match the following elements:

button elements that are disabled
input elements whose type attribute are not in the Hidden state and that are disabled
select elements that are disabled
textarea elements that are disabled
option elements that have a disabled attribute
command elements that have a disabled attribute
li elements that are children of menu elements, and that have a child element that defines a command, if the first such element's Disabled State facet is true (disabled)

:checked

The :checked pseudo-class must match the following elements:

input elements whose type attribute is in the Checkbox state and whose checkedness state is true
input elements whose type attribute is in the Radio Button state and whose checkedness state is true
command elements whose type attribute is in the Checkbox state and that have a checked attribute
command elements whose type attribute is in the Radio state and that have a checked attribute

:indeterminate

The :indeterminate pseudo-class must match input elements whose type attribute is in the Checkbox state and whose indeterminate IDL attribute is set to true.

:default

The :default pseudo-class must match the following elements:

button elements that are their form's default button
input elements whose type attribute is in the Submit Button or Image Button state, and that are their form's default button

:valid

The :valid pseudo-class must match all elements that are candidates for constraint validation and that satisfy their constraints.

:invalid

The :invalid pseudo-class must match all elements that are candidates for constraint validation but that do not satisfy their constraints.

:in-range

The :in-range pseudo-class must match all elements that are candidates for constraint validation and that are neither suffering from an underflow nor suffering from an overflow.

:out-of-range

The :out-of-range pseudo-class must match all elements that are candidates for constraint validation and that are suffering from an underflow or suffering from an overflow.

:required

The :required pseudo-class must match the following elements:

input elements that are required
textarea elements that have a required attribute

:optional

The :optional pseudo-class must match the following elements:

button elements
input elements that are not required
select elements
textarea elements that do not have a required attribute

:read-only

:read-write

The :read-write pseudo-class must match the following elements:

input elements to which the readonly attribute applies, but that are not immutable (i.e. that do not have the readonly attribute specified and that are not disabled)
textarea elements that do not have a readonly attribute, and that are not disabled
any element that is editable

The :read-only pseudo-class must match all other HTML elements.

Another section of this specification defines the target element used with the :target pseudo-class.

This specification does not define when an element matches the :hover, :focus, or :lang() dynamic pseudo-classes, as those are all defined in sufficient detail in a language-agnostic fashion in the Selectors specification. [SELECTORS]

4.15 Converting HTML to other formats

Status: Last call for comments

4.15.1 Atom

Status: Last call for comments. ISSUE-86 (atom-id-stability) blocks progress to Last Call

Given a Document source, a user agent may run the following algorithm to extract an Atom feed. This is not the only algorithm that can be used for this purpose; for instance, a user agent might instead use the hAtom algorithm. [HATOM]

If the Document source does not contain any article elements, then return nothing and abort these steps. This algorithm can only be used with documents that contain distinct articles.
Let R be an empty XML Document object whose address is user-agent defined.
Append a feed element in the Atom namespace to R.
For each meta element with a name attribute and a content attribute and whose name attribute's value is author, run the following substeps:
1. Append an author element in the Atom namespace to the root element of R.
2. Append a name element in the Atom namespace to the element created in the previous step.
3. Append a text node whose data is the value of the meta element's content attribute to the element created in the previous step.
If there is a link element whose rel attribute's value includes the keyword icon, and that element also has an href attribute whose value successfully resolves relative to the link element, then append an icon element in the Atom namespace to the root element of R whose contents is a text node with its data set to the absolute URL resulting from resolving the value of the href attribute.
Append an id element in the Atom namespace to the root element of R whose contents is a text node with its data set to the document's current address.
Optionally: Let x be a link element in the Atom namespace. Add a rel attribute whose value is the string "self" to x. Append a text node with its data set to the (user-agent-defined) address of R to x. Append x to the root element of R.

This step would be skipped when the document R has no convenient address. The presence of the rel="self" link is a "should"-level requirement in the Atom specification.
Let x be a link element in the Atom namespace. Add a rel attribute whose value is the string "alternate" to x. If the document being converted is an HTML document, add a type attribute whose value is the string "text/html" to x. Otherwise, the document being converted is an XML document; add a type attribute whose value is the string "application/xhtml+xml" to x. Append a text node with its data set to the document's current address to x. Append x to the root element of R.
Let subheading text be the empty string.
Let heading be the first element of heading content whose nearest ancestor of sectioning content is the body element, if any, or null if there is none.
Take the appropriate action from the following list, as determined by the type of the heading element:

If heading is null

Let heading text be the textContent of the title element, if there is one, or the empty string otherwise.

If heading is a hgroup element

If heading contains no child h1–h6 elements, let heading text be the empty string.

Otherwise, let headings list be a list of all the h1–h6 element children of heading, sorted first by descending rank and then in tree order (so h1s first, then h2s, etc, with each group in the order they appear in the document). Then, let heading text be the textContent of the first entry in headings list, and if there are multiple entries, let subheading text be the textContent of the second entry in headings list.

If heading is an h1–h6 element

Let heading text be the textContent of heading.
Append a title element in the Atom namespace to the root element of R whose contents is a text node with its data set to heading text.
If subheading text is not the empty string, append a subtitle element in the Atom namespace to the root element of R whose contents is a text node with its data set to subheading text.
Let global update date have no value.
For each article element article that does not have an ancestor article element, run the following steps:
1. Let E be an entry element in the Atom namespace, and append E to the root element of R.
2. Let heading be the first element of heading content whose nearest ancestor of sectioning content is article, if any, or null if there is none.
3. Take the appropriate action from the following list, as determined by the type of the heading element:
  
  If heading is null
  
  Let heading text be the empty string.
  
  If heading is a hgroup element
  
  If heading contains no child h1–h6 elements, let heading text be the empty string.
  
  Otherwise, let headings list be a list of all the h1–h6 element children of heading, sorted first by descending rank and then in tree order (so h1s first, then h2s, etc, with each group in the order they appear in the document). Then, let heading text be the textContent of the first entry in headings list.
  
  If heading is an h1–h6 element
  
  Let heading text be the textContent of heading.
4. Append a title element in the Atom namespace to E whose contents is a text node with its data set to heading text.
5. Clone article and its descendants into an environment that has scripting disabled, has no plugins, and fails any attempt to fetch any resources. Let cloned article be the resulting clone article element.
6. Remove from the subtree rooted at cloned article any article elements other than the cloned article itself, any header, footer, or nav elements whose nearest ancestor of sectioning content is the cloned article, and the first element of heading content whose nearest ancestor of sectioning content is the cloned article, if any.
7. If cloned article contains any ins or del elements with datetime attributes whose values parse as global date and time strings without errors, then let update date be the value of the datetime attribute that parses to the newest global date and time.
  
  Otherwise, let update date have no value.
  
  This value is used below; it is calculated here because in certain cases the next step mutates the cloned article.
8. If the document being converted is an HTML document, then: Let x be a content element in the Atom namespace. Add a type attribute whose value is the string "html" to x. Append a text node with its data set to the result of running the HTML fragment serialization algorithm on cloned article to x. Append x to E.
  
  Otherwise, the document being converted is an XML document: Let x be a content element in the Atom namespace. Add a type attribute whose value is the string "xml" to x. Append a div element to x. Move all the child nodes of the cloned article node to that div element, preserving their relative order. Append x to E.
9. Establish the value of id and has-alternate from the first of the following to apply:
  
  If the article node has a descendant a or area element with an href attribute that successfully resolves relative to that descendant and a rel attribute whose value includes the bookmark keyword
  
  Let id be the absolute URL resulting from resolving the value of the href attribute of the first such a or area element, relative to the element. Let has-alternate be true.
  
  If the article node has an id attribute
  
  Let id be the document's current address, with the fragment identifier (if any) removed, and with a new fragment identifier specified, consisting of the value of the article element's id attribute. Let has-alternate be false.
  
  Otherwise
  
  Let id be a user-agent-defined undereferenceable yet globally unique valid absolute URL. The same absolute URL should be generated for each run of this algorithm when given the same input. Let has-alternate be false.
10. Append an id element in the Atom namespace to E whose contents is a text node with its data set to id.
11. If has-alternate is true: Let x be a link element in the Atom namespace. Add a rel attribute whose value is the string "alternate" to x. Append a text node with its data set to id to x. Append x to E.
12. If article has a time element descendant that has a pubdate attribute and whose nearest ancestor article element is article, and the first such element's date is not unknown, then run the following substeps, with e being the first such element:
  1. Let datetime be a global date and time whose date component is the date of e.
  2. If e's time and time-zone offset are not unknown, then let datetime's time and time-zone offset components be the time and time-zone offset of e. Otherwise, let them be midnight and no offset respectively ("00:00Z").
  3. Let publication date be the best representation of the global date and time string datetime.
  Otherwise, let publication date have no value.
13. If update date has no value but publication date does, then let update date have the value of publication date.
  
  Otherwise, if publication date has no value but update date does, then let publication date have the value of update date.
14. If update date has a value, and global update date has no value or is less recent than update date, then let global update date have the value of update date.
15. If publication date and update date both still have no value, then let them both value a value that is a valid global date and time string representing the global date and time of the moment that this algorithm was invoked.
16. Append an published element in the Atom namespace to E whose contents is a text node with its data set to publication date.
17. Append an updated element in the Atom namespace to E whose contents is a text node with its data set to update date.
If global update date has no value, then let it have a value that is a valid global date and time string representing the global date and time of the date and time of the Document's source file's last modification, if it is known, or else of the moment that this algorithm was invoked.
Insert an updated element in the Atom namespace into the root element of R before the first entry in the Atom namespace whose contents is a text node with its data set to global update date.
Return the Atom document R.

The above algorithm does not guarantee that the output will be a conforming Atom feed. In particular, if insufficient information is provided in the document (e.g. if the document does not have any <meta name="author" content="..."> elements), then the output will not be conforming.

The Atom namespace is: http://www.w3.org/2005/Atom

5 Loading Web pages

Status: Last call for comments. ISSUE-94 (webcoresplit) blocks progress to Last Call

This section describes features that apply most directly to Web browsers. Having said that, except where specified otherwise, the requirements defined in this section do apply to all user agents, whether they are Web browsers or not.

5.1 Browsing contexts

Status: Last call for comments

A browsing context is an environment in which Document objects are presented to the user.

A tab or window in a Web browser typically contains a browsing context, as does an iframe or frames in a frameset.

Each browsing context has a corresponding WindowProxy object.

A browsing context has a session history, which lists the Document objects that that browsing context has presented, is presenting, or will present. At any time, one Document in each browsing context is designated the active document.

Each Document has a collection of one or more views.

A view is a user agent interface tied to a particular media used for the presentation of a particular Document object in some media. A view may be interactive. Each view is represented by an AbstractView object. [DOMVIEWS]

The main view through which a user primarily interacts with a user agent is the default view. The AbstractView object that represents this view must also implement the Window interface, and is referred to as the Document's Window object. WindowProxy objects forward everything to the active document's default view's Window object.

The defaultView attribute on the Document object's DocumentView interface must return the browsing context's WindowProxy object, not the actual AbstractView object of the default view. [DOMVIEWS]

The document attribute of an AbstractView object representing a view gives the view's corresponding Document object. [DOMVIEWS]

In general, there is a 1-to-1 mapping from the Window object to the Document object. In one particular case, a set of views can be reused for the presentation of a second Document in the same browsing context, such that the mapping is then 2-to-1. This occurs when a browsing context is navigated from the initial about:blank Document to another, with replacement enabled.

Events that use the UIEvent interface are related to a specific view (the view in which the event happened); when that view is the default view, the event object's view attribute's must return the WindowProxy object of the browsing context of that view, not the actual AbstractView object of the default view. [DOMEVENTS]

A typical Web browser has one obvious view per Document: the browser's window (screen media). This is typically the default view. If a page is printed, however, a second view becomes evident, that of the print media. The two views always share the same underlying Document object, but they have a different presentation of that object. A speech browser might have a different default view, using the speech media.

A Document does not necessarily have a browsing context associated with it. In particular, data mining tools are likely to never instantiate browsing contexts.

A browsing context can have a creator browsing context, the browsing context that was responsible for its creation. If a browsing context has a parent browsing context, then that is its creator browsing context. Otherwise, if the browsing context has an opener browsing context, then that is its creator browsing context. Otherwise, the browsing context has no creator browsing context.

If a browsing context A has a creator browsing context, then the Document that was the active document of that creator browsing context at the time A was created is the creator Document.

When a browsing context is first created, it must be created with a single Document in its session history, whose address is about:blank, which is marked as being an HTML document, and whose character encoding is UTF-8. The Document must have a single child html node, which itself has a single child body node.

If the browsing context is created specifically to be immediately navigated, then that initial navigation will have replacement enabled.

The origin of the about:blank Document is set when the Document is created. If the new browsing context has a creator browsing context, then the origin of the about:blank Document is the origin of the creator Document. Otherwise, the origin of the about:blank Document is a globally unique identifier assigned when the new browsing context is created.

5.1.1 Nested browsing contexts

Status: Last call for comments

Certain elements (for example, iframe elements) can instantiate further browsing contexts. These are called nested browsing contexts. If a browsing context P has an element E in one of its Documents D that nests another browsing context C inside it, then P is said to be the parent browsing context of C, C is said to be a child browsing context of P, C is said to be nested through D, and E is said to be the browsing context container of C.

A browsing context A is said to be an ancestor of a browsing context B if there exists a browsing context A' that is a child browsing context of A and that is itself an ancestor of B, or if there is a browsing context P that is a child browsing context of A and that is the parent browsing context of B.

The browsing context with no parent browsing context is the top-level browsing context of all the browsing contexts nested within it (either directly or indirectly through other nested browsing contexts).

The transitive closure of parent browsing contexts for a nested browsing context gives the list of ancestor browsing contexts.

The list of the descendant browsing contexts of a Document d is the list returned by the following algorithm:

Let list be an empty list.
For each child browsing context of d that is nested through an element that is in the Document d, in the tree order of the elements of the elements nesting those browsing contexts, append to the list list the list of the descendant browsing contexts of the active document of that child browsing context.
Return the constructed list.

A Document is said to be fully active when it is the active document of its browsing context, and either its browsing context is a top-level browsing context, or the Document through which that browsing context is nested is itself fully active.

Because they are nested through an element, child browsing contexts are always tied to a specific Document in their parent browsing context. User agents must not allow the user to interact with child browsing contexts of elements that are in Documents that are not themselves fully active.

A nested browsing context can have a seamless browsing context flag set, if it is embedded through an iframe element with a seamless attribute.

5.1.1.1 Navigating nested browsing contexts in the DOM

Status: Last call for comments

window . top

Returns the WindowProxy for the top-level browsing context.

window . parent

Returns the WindowProxy for the parent browsing context.

window . frameElement

Returns the Element for the browsing context container.

Returns null if there isn't one.

Throws a SECURITY_ERR exception in cross-origin situations.

The top IDL attribute on the Window object of a Document in a browsing context b must return the WindowProxy object of its top-level browsing context (which would be its own WindowProxy object if it was a top-level browsing context itself).

The parent IDL attribute on the Window object of a Document in a browsing context b must return the WindowProxy object of the parent browsing context, if there is one (i.e. if b is a child browsing context), or the WindowProxy object of the browsing context b itself, otherwise (i.e. if it is a top-level browsing context).

The frameElement IDL attribute on the Window object of a Document d, on getting, must run the following algorithm:

If d is not a Document in a child browsing context, return null and abort these steps.
If the parent browsing context's active document does not have the same effective script origin as the entry script, then throw a SECURITY_ERR exception.
Otherwise, return the browsing context container for b.

5.1.2 Auxiliary browsing contexts

Status: Last call for comments

It is possible to create new browsing contexts that are related to a top-level browsing context without being nested through an element. Such browsing contexts are called auxiliary browsing contexts. Auxiliary browsing contexts are always top-level browsing contexts.

An auxiliary browsing context has an opener browsing context, which is the browsing context from which the auxiliary browsing context was created, and it has a furthest ancestor browsing context, which is the top-level browsing context of the opener browsing context when the auxiliary browsing context was created.

5.1.2.1 Navigating auxiliary browsing contexts in the DOM

Status: Last call for comments

The opener IDL attribute on the Window object must return the WindowProxy object of the browsing context from which the current browsing context was created (its opener browsing context), if there is one and it is still available.

5.1.3 Secondary browsing contexts

Status: Last call for comments

User agents may support secondary browsing contexts, which are browsing contexts that form part of the user agent's interface, apart from the main content area.

5.1.4 Security

Status: Last call for comments

A browsing context A is allowed to navigate a second browsing context B if one of the following conditions is true:

Either the origin of the active document of A is the same as the origin of the active document of B, or
The browsing context A is a nested browsing context and its top-level browsing context is B, or
The browsing context B is an auxiliary browsing context and A is allowed to navigate B's opener browsing context, or
The browsing context B is not a top-level browsing context, but there exists an ancestor browsing context of B whose active document has the same origin as the active document of A (possibly in fact being A itself).

An element has a browsing context scope origin if its Document's browsing context is a top-level browsing context or if all of its Document's ancestor browsing contexts all have active documents whose origin are the same origin as the element's Document's origin. If an element has a browsing context scope origin, then its value is the origin of the element's Document.

5.1.5 Groupings of browsing contexts

Status: Last call for comments

Each browsing context is defined as having a list of zero or more directly reachable browsing contexts. These are:

All the browsing context's child browsing contexts.
The browsing context's parent browsing context.
All the browsing contexts that have the browsing context as their opener browsing context.
The browsing context's opener browsing context.

The transitive closure of all the browsing contexts that are directly reachable browsing contexts forms a unit of related browsing contexts.

Each unit of related browsing contexts is then further divided into the smallest number of groups such that every member of each group has an effective script origin that, through appropriate manipulation of the document.domain attribute, could be made to be the same as other members of the group, but could not be made the same as members of any other group. Each such group is a unit of related similar-origin browsing contexts.

Each unit of related similar-origin browsing contexts can have a entry script which is used to obtain, amongst other things, the script's base URL to resolve relative URLs used in scripts running in that unit of related similar-origin browsing contexts. Initially, there is no entry script.

There is at most one event loop per unit of related similar-origin browsing contexts.

5.1.6 Browsing context names

Status: Last call for comments

Browsing contexts can have a browsing context name. By default, a browsing context has no name (its name is not set).

A valid browsing context name is any string with at least one character that does not start with a U+005F LOW LINE character. (Names starting with an underscore are reserved for special keywords.)

A valid browsing context name or keyword is any string that is either a valid browsing context name or that is an ASCII case-insensitive match for one of: _blank, _self, _parent, or _top.

The rules for choosing a browsing context given a browsing context name are as follows. The rules assume that they are being applied in the context of a browsing context.

If the given browsing context name is the empty string or _self, then the chosen browsing context must be the current one.
If the given browsing context name is _parent, then the chosen browsing context must be the parent browsing context of the current one, unless there isn't one, in which case the chosen browsing context must be the current browsing context.
If the given browsing context name is _top, then the chosen browsing context must be the most top-level browsing context of the current one.
If the given browsing context name is not _blank and there exists a browsing context whose name is the same as the given browsing context name, and the current browsing context is allowed to navigate that browsing context, and the user agent determines that the two browsing contexts are related enough that it is ok if they reach each other, then that browsing context must be the chosen one. If there are multiple matching browsing contexts, the user agent should select one in some arbitrary consistent manner, such as the most recently opened, most recently focused, or more closely related.
Otherwise, a new browsing context is being requested, and what happens depends on the user agent's configuration and/or abilities:

If the current browsing context had the sandboxed navigation browsing context flag set when its active document was created.

The user agent may offer to create a new top-level browsing context or reuse an existing top-level browsing context. If the user picks one of those options, then the designated browsing context must be the chosen one (the browsing context's name isn't set to the given browsing context name). Otherwise (if the user agent doesn't offer the option to the user, or if the user declines to allow a browsing context to be used) there must not be a chosen browsing context.

If the user agent has been configured such that in this instance it will create a new browsing context, and the browsing context is being requested as part of following a hyperlink whose link types include the noreferrer keyword

A new top-level browsing context must be created. If the given browsing context name is not _blank, then the new top-level browsing context's name must be the given browsing context name (otherwise, it has no name). The chosen browsing context must be this new browsing context.

If it is immediately navigated, then the navigation will be done with replacement enabled.

If the user agent has been configured such that in this instance it will create a new browsing context, and the noreferrer keyword doesn't apply

A new auxiliary browsing context must be created, with the opener browsing context being the current one. If the given browsing context name is not _blank, then the new auxiliary browsing context's name must be the given browsing context name (otherwise, it has no name). The chosen browsing context must be this new browsing context.

If it is immediately navigated, then the navigation will be done with replacement enabled.

If the user agent has been configured such that in this instance it will reuse the current browsing context

The chosen browsing context is the current browsing context.

If the user agent has been configured such that in this instance it will not find a browsing context

There must not be a chosen browsing context.

User agent implementors are encouraged to provide a way for users to configure the user agent to always reuse the current browsing context.

5.2 The `Window` object

Status: Last call for comments

[OverrideBuiltins, ReplaceableNamedProperties] 
interface Window {
  // the current browsing context
  readonly attribute WindowProxy window;
  readonly attribute WindowProxy self;
           attribute DOMString name;
  [PutForwards=href] readonly attribute Location location;
  readonly attribute History history;
  readonly attribute UndoManager undoManager;
  Selection getSelection();
  [Replaceable] readonly attribute BarProp locationbar;
  [Replaceable] readonly attribute BarProp menubar;
  [Replaceable] readonly attribute BarProp personalbar;
  [Replaceable] readonly attribute BarProp scrollbars;
  [Replaceable] readonly attribute BarProp statusbar;
  [Replaceable] readonly attribute BarProp toolbar;
  void close();
  void focus();
  void blur();

  // other browsing contexts
  [Replaceable] readonly attribute WindowProxy frames;
  [Replaceable] readonly attribute unsigned long length;
  readonly attribute WindowProxy top;
  [Replaceable] readonly attribute WindowProxy opener;
  readonly attribute WindowProxy parent;
  readonly attribute Element frameElement;
  WindowProxy open(in optional DOMString url, in optional DOMString target, in optional DOMString features, in optional DOMString replace);
  getter WindowProxy (in unsigned long index);
  getter WindowProxy (in DOMString name);

  // the user agent
  readonly attribute Navigator navigator; 
  readonly attribute ApplicationCache applicationCache;

  // user prompts
  void alert(in DOMString message);
  boolean confirm(in DOMString message);
  DOMString prompt(in DOMString message, in optional DOMString default);
  void print();
  any showModalDialog(in DOMString url, in optional any argument);

  // event handler IDL attributes
           attribute Function onabort;
           attribute Function onafterprint;
           attribute Function onbeforeprint;
           attribute Function onbeforeunload;
           attribute Function onblur;
           attribute Function oncanplay;
           attribute Function oncanplaythrough;
           attribute Function onchange;
           attribute Function onclick;
           attribute Function oncontextmenu;
           attribute Function ondblclick;
           attribute Function ondrag;
           attribute Function ondragend;
           attribute Function ondragenter;
           attribute Function ondragleave;
           attribute Function ondragover;
           attribute Function ondragstart;
           attribute Function ondrop;
           attribute Function ondurationchange;
           attribute Function onemptied;
           attribute Function onended;
           attribute Function onerror;
           attribute Function onfocus;
           attribute Function onformchange;
           attribute Function onforminput;
           attribute Function onhashchange;
           attribute Function oninput;
           attribute Function oninvalid;
           attribute Function onkeydown;
           attribute Function onkeypress;
           attribute Function onkeyup;
           attribute Function onload;
           attribute Function onloadeddata;
           attribute Function onloadedmetadata;
           attribute Function onloadstart;
           attribute Function onmessage;
           attribute Function onmousedown;
           attribute Function onmousemove;
           attribute Function onmouseout;
           attribute Function onmouseover;
           attribute Function onmouseup;
           attribute Function onmousewheel;
           attribute Function onoffline;
           attribute Function ononline;
           attribute Function onpause;
           attribute Function onplay;
           attribute Function onplaying;
           attribute Function onpagehide;
           attribute Function onpageshow;
           attribute Function onpopstate;
           attribute Function onprogress;
           attribute Function onratechange;
           attribute Function onreadystatechange;
           attribute Function onredo;
           attribute Function onresize;
           attribute Function onscroll;
           attribute Function onseeked;
           attribute Function onseeking;
           attribute Function onselect;
           attribute Function onshow;
           attribute Function onstalled;
           attribute Function onstorage;
           attribute Function onsubmit;
           attribute Function onsuspend;
           attribute Function ontimeupdate;
           attribute Function onundo;
           attribute Function onunload;
           attribute Function onvolumechange;
           attribute Function onwaiting;
};
Window implements EventTarget;

window . window
window . frames
window . self: These attributes all return window.

The window, frames, and self IDL attributes must all return the Window object's browsing context's WindowProxy object.

5.2.1 Security

Status: Last call for comments

User agents must raise a SECURITY_ERR exception whenever any of the members of a Window object are accessed by scripts whose effective script origin is not the same as the Window object's Document's effective script origin, with the following exceptions:

The location object
The postMessage() method with two arguments
The postMessage() method with three arguments
The frames attribute
The dynamic nested browsing context properties

When a script whose effective script origin is not the same as the Window object's Document's effective script origin attempts to access that Window object's methods or attributes, the user agent must act as if any changes to the Window object's properties, getters, setters, etc, were not present.

For members that return objects (including function objects), each distinct effective script origin that is not the same as the Window object's Document's effective script origin must be provided with a separate set of objects. These objects must have the prototype chain appropriate for the script for which the objects are created (not those that would be appropriate for scripts whose script's global object is the Window object in question).

For instance, if two frames containing Documents from different origins access the same Window object's postMessage() method, they will get distinct objects that are not equal.

5.2.2 APIs for creating and navigating browsing contexts by name

Status: Last call for comments

window = window . open( [ url [, target [, features [, replace ] ] ] ] )

Opens a window to show url (defaults to about:blank), and returns it. The target argument gives the name of the new window. If a window exists with that name already, it is reused. The replace attribute, if true, means that whatever page is currently open in that window will be removed from the window's session history. The features argument is ignored.

window . name [ = value ]

Returns the name of the window.

Can be set, to change the name.

window . close()

Closes the window.

The open() method on Window objects provides a mechanism for navigating an existing browsing context or opening and navigating an auxiliary browsing context.

The method has four arguments, though they are all optional.

The first argument, url, must be a valid URL for a page to load in the browsing context. If no arguments are provided, or if the first argument is the empty string, then the url argument defaults to "about:blank". The argument must be resolved to an absolute URL (or an error), relative to the entry script's base URL, when the method is invoked.

The second argument, target, specifies the name of the browsing context that is to be navigated. It must be a valid browsing context name or keyword. If fewer than two arguments are provided, then the name argument defaults to the value "_blank".

The third argument, features, has no effect and is supported for historical reasons only.

The fourth argument, replace, specifies whether or not the new page will replace the page currently loaded in the browsing context, when target identifies an existing browsing context (as opposed to leaving the current page in the browsing context's session history). When three or fewer arguments are provided, replace defaults to false.

When the method is invoked, the user agent must first select a browsing context to navigate by applying the rules for choosing a browsing context given a browsing context name using the target argument as the name and the browsing context of the script as the context in which the algorithm is executed, unless the user has indicated a preference, in which case the browsing context to navigate may instead be the one indicated by the user.

For example, suppose there is a user agent that supports control-clicking a link to open it in a new tab. If a user clicks in that user agent on an element whose onclick handler uses the window.open() API to open a page in an iframe, but, while doing so, holds the control key down, the user agent could override the selection of the target browsing context to instead target a new tab.

Then, the user agent must navigate the selected browsing context to the absolute URL (or error) obtained from resolving url earlier. If the replace is true, then replacement must be enabled; otherwise, it must not be enabled unless the browsing context was just created as part of the rules for choosing a browsing context given a browsing context name. The navigation must be done with the browsing context of the entry script as the source browsing context.

The method must return the WindowProxy object of the browsing context that was navigated, or null if no browsing context was navigated.

The name attribute of the Window object must, on getting, return the current name of the browsing context, and, on setting, set the name of the browsing context to the new value.

The name gets reset when the browsing context is navigated to another domain.

The close() method on Window objects should, if the corresponding browsing context A is an auxiliary browsing context that was created by a script (as opposed to by an action of the user), and if the browsing context of the script that invokes the method is allowed to navigate the browsing context A, close the browsing context A (and may discard it too).

5.2.3 Accessing other browsing contexts

Status: Last call for comments

window . length: Returns the number of child browsing contexts.
window[index]: Returns the indicated child browsing context.

The length IDL attribute on the Window interface must return the number of child browsing contexts that are nested through elements that are in the Document that is the active document of that Window object, if that Window's browsing context shares the same event loop as the script's browsing context of the entry script accessing the IDL attribute; otherwise, it must return zero.

The indices of the supported indexed properties on the Window object at any instant are the numbers in the range 0 .. n-1, where n is the number returned by the length IDL attribute. If n is zero then there are no supported indexed properties.

When a Window object is indexed to retrieve an indexed property index, the value returned must be the indexth child browsing context of the Document that is nested through an element that is in the Document, sorted in the tree order of the elements nesting those browsing contexts.

These properties are the dynamic nested browsing context properties.

5.2.4 Named access on the `Window` object

Status: Last call for comments

window[name]: Returns the indicated child browsing context.

The Window interface supports named properties. The names of the supported named properties at any moment consist of:

The value of the name content attribute for all a, applet, area, embed, frame, frameset, form, iframe, img, and object elements in the active document that have a name content attribute, and,
The value of the id content attribute of any HTML element in the active document with an id content attribute.

When the Window object is indexed for property retrieval using a name name, then the user agent must return the value obtained using the following steps:

Let elements be the list of named elements with the name name in the active document.
There will be at least one such element, by definition.
If elements contains an iframe element, then return the WindowProxy object of the nested browsing context represented by the first such iframe element in tree order, and abort these steps.
Otherwise, if elements has only one element, return that element and abort these steps.
Otherwise return an HTMLCollection rooted at the Document node, whose filter matches only named elements with the name name.

Named elements with the name name, for the purposes of the above algorithm, are those that are either:

a, applet, area, embed, form, frame, frameset, iframe, img, or object elements that have a name content attribute whose value is name, or
HTML elements elements that have an id content attribute whose value is name.

5.2.5 Garbage collection and browsing contexts

Status: Last call for comments

A browsing context has a strong reference to each of its Documents and its WindowProxy object, and the user agent itself has a strong reference to its top-level browsing contexts.

A Document has a strong reference to each of its views and their AbstractView objects.

Each script has a strong reference to its browsing context and its document.

When a browsing context is to discard a Document, the user agent must run the following steps:

Set the Document's salvageable state to false.
Run any unloading document cleanup steps for the Document that are defined by this specification or any other relevant specifications.
Remove any tasks associated with the Document in any task source, without running those tasks.
Discard all the child browsing contexts of the Document.
Lose the strong reference from the Document's browsing context to the Document.

The browsing context's default view's Window object has a strong reference to its Document object through the document attribute of the AbstractView interface. Thus, references from other scripts to either of those objects will keep both alive. [DOMVIEWS]

Whenever a Document object is discarded, it is also removed from the list of the worker's Documents of each worker whose list contains that Document.

When a browsing context is discarded, the strong reference from the user agent itself to the browsing context must be severed, and all the Document objects for all the entries in the browsing context's session history must be discarded as well.

User agents may discard top-level browsing contexts at any time (typically, in response to user requests, e.g. when a user closes a window containing one or more top-level browsing contexts). Other browsing contexts must be discarded once their WindowProxy object is eligible for garbage collection.

5.2.6 Browser interface elements

Status: Last call for comments

To allow Web pages to integrate with Web browsers, certain Web browser interface elements are exposed in a limited way to scripts in Web pages.

Each interface element is represented by a BarProp object:

interface BarProp {
           attribute boolean visible;
};

window . locationbar . visible: Returns true if the location bar is visible; otherwise, returns false.
window . menubar . visible: Returns true if the menu bar is visible; otherwise, returns false.
window . personalbar . visible: Returns true if the personal bar is visible; otherwise, returns false.
window . scrollbars . visible: Returns true if the scroll bars are visible; otherwise, returns false.
window . statusbar . visible: Returns true if the status bar is visible; otherwise, returns false.
window . toolbar . visible: Returns true if the toolbar is visible; otherwise, returns false.

The visible attribute, on getting, must return either true or a value determined by the user agent to most accurately represent the visibility state of the user interface element that the object represents, as described below. On setting, the new value must be discarded.

The following BarProp objects exist for each Document object in a browsing context. Some of the user interface elements represented by these objects might have no equivalent in some user agents; for those user agents, except when otherwise specified, the object must act as if it was present and visible (i.e. its visible attribute must return true).

The location bar BarProp object: Represents the user interface element that contains a control that displays the URL of the active document, or some similar interface concept.
The menu bar BarProp object: Represents the user interface element that contains a list of commands in menu form, or some similar interface concept.
The personal bar BarProp object: Represents the user interface element that contains links to the user's favorite pages, or some similar interface concept.
The scrollbar BarProp object: Represents the user interface element that contains a scrolling mechanism, or some similar interface concept.
The status bar BarProp object: Represents a user interface element found immediately below or after the document, as appropriate for the default view's media. If the user agent has no such user interface element, then the object may act as if the corresponding user interface element was absent (i.e. its visible attribute may return false).
The toolbar BarProp object: Represents the user interface element found immediately above or before the document, as appropriate for the default view's media. If the user agent has no such user interface element, then the object may act as if the corresponding user interface element was absent (i.e. its visible attribute may return false).

The locationbar attribute must return the location bar BarProp object.

The menubar attribute must return the menu bar BarProp object.

The personalbar attribute must return the personal bar BarProp object.

The scrollbars attribute must return the scrollbar BarProp object.

The statusbar attribute must return the status bar BarProp object.

The toolbar attribute must return the toolbar BarProp object.

5.2.7 The `WindowProxy` object

Status: Last call for comments

As mentioned earlier, each browsing context has a WindowProxy object. This object is unusual in that all operations that would be performed on it must be performed on the Window object of the browsing context's active document instead. It is thus indistinguishable from that Window object in every way until the browsing context is navigated.

There is no WindowProxy interface object.

The WindowProxy object allows scripts to act as if each browsing context had a single Window object, while still keeping separate Window objects for each Document.

In the following example, the variable x is set to the WindowProxy object returned by the window accessor on the global object. All of the expressions following the assignment return true, because in every respect, the WindowProxy object acts like the underlying Window object.

var x = window;
x instanceof Window; // true
x === this; // true

5.3 Origin

Status: Last call for comments

The origin of a resource and the effective script origin of a resource are both either opaque identifiers or tuples consisting of a scheme component, a host component, a port component, and optionally extra data.

The extra data could include the certificate of the site when using encrypted connections, to ensure that if the site's secure certificate changes, the origin is considered to change as well.

These characteristics are defined as follows:

For URLs

The origin and effective script origin of the URL is whatever is returned by the following algorithm:

Let url be the URL for which the origin is being determined.
Parse url.
If url identifies a resource that is its own trust domain (e.g. it identifies an e-mail on an IMAP server or a post on an NNTP server) then return a globally unique identifier specific to the resource identified by url, so that if this algorithm is invoked again for URLs that identify the same resource, the same identifier will be returned.
If url does not use a server-based naming authority, or if parsing url failed, or if url is not an absolute URL, then return a new globally unique identifier.
Let scheme be the <scheme> component of url, converted to ASCII lowercase.
If the UA doesn't support the protocol given by scheme, then return a new globally unique identifier.
If scheme is "file", then the user agent may return a UA-specific value.
Let host be the <host> component of url.
Apply the IDNA ToASCII algorithm to host, with both the AllowUnassigned and UseSTD3ASCIIRules flags set. Let host be the result of the ToASCII algorithm.

If ToASCII fails to convert one of the components of the string, e.g. because it is too long or because it contains invalid characters, then return a new globally unique identifier. [RFC3490]
Let host be the result of converting host to ASCII lowercase.
If there is no <port> component, then let port be the default port for the protocol given by scheme. Otherwise, let port be the <port> component of url.
Return the tuple (scheme, host, port).

In addition, if the URL is in fact associated with a Document object that was created by parsing the resource obtained from fetching URL, and this was done over a secure connection, then the server's secure certificate may be added to the origin as additional data.

For scripts

The origin and effective script origin of a script are determined from another resource, called the owner:

If a script is in a script element: The owner is the Document to which the script element belongs.
If a script is in an event handler content attribute: The owner is the Document to which the attribute node belongs.
If a script is a function or other code reference created by another script: The owner is the script that created it.
If a script is a javascript: URL that was returned as the location of an HTTP redirect (or equivalent in other protocols): The owner is the URL that redirected to the javascript: URL.
If a script is a javascript: URL in an attribute: The owner is the Document of the element on which the attribute is found.
If a script is a javascript: URL in a style sheet: The owner is the URL of the style sheet.
If a script is a javascript: URL to which a browsing context is being navigated, the URL having been provided by the user (e.g. by using a bookmarklet): The owner is the Document of the browsing context's active document.
If a script is a javascript: URL to which a browsing context is being navigated, the URL having been declared in markup: The owner is the Document of the element (e.g. an a or area element) that declared the URL.
If a script is a javascript: URL to which a browsing context is being navigated, the URL having been provided by script: The owner is the script that provided the URL.

The origin of the script is then equal to the origin of the owner, and the effective script origin of the script is equal to the effective script origin of the owner.

For Document objects and images

If a Document is in a browsing context whose sandboxed origin browsing context flag was set when the Document was created
If a Document was generated from a resource labeled as text/html-sandboxed: The origin is a globally unique identifier assigned when the Document is created.
If a Document or image was returned by the XMLHttpRequest API: The origin is equal to the XMLHttpRequest origin of the XMLHttpRequest object. [XHR]
If a Document or image was generated from a javascript: URL: The origin is equal to the origin of the script of that javascript: URL.
If a Document or image was served over the network and has an address that uses a URL scheme with a server-based naming authority: The origin is the origin of the address of the Document or the URL of the image, as appropriate.
If a Document or image was generated from a data: URL that was returned as the location of an HTTP redirect (or equivalent in other protocols): The origin is the origin of the URL that redirected to the data: URL.
If a Document or image was generated from a data: URL found in another Document or in a script: The origin is the origin of the Document or script that initiated the navigation to that URL.
If a Document has the address "about:blank": The origin of the Document is the origin it was assigned when its browsing context was created.
If a Document is an iframe srcdoc document: The origin of the Document is the origin of the Document's browsing context's browsing context container's Document.
If a Document or image was obtained in some other manner (e.g. a data: URL typed in by the user, a Document created using the createDocument() API, etc): The origin is a globally unique identifier assigned when the Document or image is created.

When a Document is created, its effective script origin is initialized to the origin of the Document. However, the document.domain attribute can be used to change it.

For audio and video elements

If value of the media element's currentSrc attribute is the empty string, the origin is the same as the origin of the element's Document's origin.

Otherwise, the origin is equal to the origin of the absolute URL given by the media element's currentSrc attribute.

The Unicode serialization of an origin is the string obtained by applying the following algorithm to the given origin:

If the origin in question is not a scheme/host/port tuple, then return the literal string "null" and abort these steps.
Otherwise, let result be the scheme part of the origin tuple.
Append the string "://" to result.
Apply the IDNA ToUnicode algorithm to each component of the host part of the origin tuple, and append the results — each component, in the same order, separated by U+002E FULL STOP characters (.) — to result. [RFC3490]
If the port part of the origin tuple gives a port that is different from the default port for the protocol given by the scheme part of the origin tuple, then append a U+003A COLON character (:) and the given port, in base ten, to result.
Return result.

The ASCII serialization of an origin is the string obtained by applying the following algorithm to the given origin:

If the origin in question is not a scheme/host/port tuple, then return the literal string "null" and abort these steps.
Otherwise, let result be the scheme part of the origin tuple.
Append the string "://" to result.
Apply the IDNA ToASCII algorithm the host part of the origin tuple, with both the AllowUnassigned and UseSTD3ASCIIRules flags set, and append the results result.

If ToASCII fails to convert one of the components of the string, e.g. because it is too long or because it contains invalid characters, then return the empty string and abort these steps. [RFC3490]
If the port part of the origin tuple gives a port that is different from the default port for the protocol given by the scheme part of the origin tuple, then append a U+003A COLON character (:) and the given port, in base ten, to result.
Return result.

Two origins are said to be the same origin if the following algorithm returns true:

Let A be the first origin being compared, and B be the second origin being compared.
If A and B are both opaque identifiers, and their value is equal, then return true.
Otherwise, if either A or B or both are opaque identifiers, return false.
If A and B have scheme components that are not identical, return false.
If A and B have host components that are not identical, return false.
If A and B have port components that are not identical, return false.
If either A or B have additional data, but that data is not identical for both, return false.
Return true.

5.3.1 Relaxing the same-origin restriction

Status: Last call for comments

document . domain [ = domain ]

Returns the current domain used for security checks.

Can be set to a value that removes subdomains, to change the effective script origin to allow pages on other subdomains of the same domain (if they do the same thing) to access each other.

The domain attribute on Document objects must be initialized to the document's domain, if it has one, and the empty string otherwise. If the value is an IPv6 address, then the square brackets from the host portion of the <host> component must be omitted from the attribute's value.

On getting, the attribute must return its current value, unless the document was created by XMLHttpRequest, in which case it must throw an INVALID_ACCESS_ERR exception.

On setting, the user agent must run the following algorithm:

If the document was created by XMLHttpRequest, throw an INVALID_ACCESS_ERR exception and abort these steps.
If the new value is an IP address, let new value be the new value. Otherwise, apply the IDNA ToASCII algorithm to the new value, with both the AllowUnassigned and UseSTD3ASCIIRules flags set, and let new value be the result of the ToASCII algorithm.

If ToASCII fails to convert one of the components of the string, e.g. because it is too long or because it contains invalid characters, then throw a SECURITY_ERR exception and abort these steps. [RFC3490]
If new value is not exactly equal to the current value of the document.domain attribute, then run these substeps:
1. If the current value is an IP address, throw a SECURITY_ERR exception and abort these steps.
2. If new value, prefixed by a U+002E FULL STOP (.), does not exactly match the end of the current value, throw a SECURITY_ERR exception and abort these steps.
3. If new value matches a suffix in the Public Suffix List, or, if new value, prefixed by a U+002E FULL STOP (.), matches the end of a suffix in the Public Suffix List, then throw a SECURITY_ERR exception and abort these steps. [PSL]
  
  Suffixes must be compared after applying the IDNA ToASCII algorithm to them, with both the AllowUnassigned and UseSTD3ASCIIRules flags set, in an ASCII case-insensitive manner. [RFC3490]
Release the storage mutex.
Set the attribute's value to new value.
Set the host part of the effective script origin tuple of the Document to new value.
Set the port part of the effective script origin tuple of the Document to "manual override" (a value that, for the purposes of comparing origins, is identical to "manual override" but not identical to any other value).

The domain of a Document is the host part of the document's origin, if that is a scheme/host/port tuple. If it isn't, then the document does not have a domain.

The domain attribute is used to enable pages on different hosts of a domain to access each others' DOMs.

Do not use the document.domain attribute when using shared hosting. If an untrusted third party is able to host an HTTP server at the same IP address but on a different port, then the same-origin protection that normally protects two different sites on the same host will fail, as the ports are ignored when comparing origins after the document.domain attribute has been used.

5.4 Session history and navigation

Status: Last call for comments

5.4.1 The session history of browsing contexts

Status: Last call for comments

The sequence of Documents in a browsing context is its session history.

History objects provide a representation of the pages in the session history of browsing contexts. Each browsing context, including nested browsing contexts, has a distinct session history.

Each Document object in a browsing context's session history is associated with a unique instance of the History object, although they all must model the same underlying session history.

The history attribute of the Window interface must return the object implementing the History interface for that Window object's Document.

History objects represent their browsing context's session history as a flat list of session history entries. Each session history entry consists of either a URL or a state object, or both, and may in addition have a title, a Document object, form data, a scroll position, and other information associated with it.

This does not imply that the user interface need be linear. See the notes below.

Titles associated with session history entries need not have any relation with the current title of the Document. The title of a session history entry is intended to explain the state of the document at that point, so that the user can navigate the document's history.

URLs without associated state objects are added to the session history as the user (or script) navigates from page to page.

A state object is an object representing a user interface state.

Pages can add state objects between their entry in the session history and the next ("forward") entry. These are then returned to the script when the user (or script) goes back in the history, thus enabling authors to use the "navigation" metaphor even in one-page applications.

At any point, one of the entries in the session history is the current entry. This is the entry representing the active document of the browsing context. The current entry is usually an entry for the location of the Document. However, it can also be one of the entries for state objects added to the history by that document.

Entries that consist of state objects share the same Document as the entry for the page that was active when they were added.

Contiguous entries that differ just by fragment identifier also share the same Document.

All entries that share the same Document (and that are therefore merely different states of one particular document) are contiguous by definition.

User agents may discard the Document objects of entries other than the current entry that are not referenced from any script, reloading the pages afresh when the user or script navigates back to such pages. This specification does not specify when user agents should discard Document objects and when they should cache them.

Entries that have had their Document objects discarded must, for the purposes of the algorithms given below, act as if they had not. When the user or script navigates back or forwards to a page which has no in-memory DOM objects, any other entries that shared the same Document object with it must share the new object as well.

5.4.2 The `History` interface

Status: Last call for comments

interface History {
  readonly attribute long length;
  void go(in optional long delta);
  void back();
  void forward();
  void pushState(in any data, in DOMString title, in optional DOMString url);
  void replaceState(in any data, in DOMString title, in optional DOMString url);
};

window . history . length

Returns the number of entries in the joint session history.

window . history . go( [ delta ] )

Goes back or forward the specified number of steps in the joint session history.

A zero delta will reload the current page.

If the delta is out of range, does nothing.

window . history . back()

Goes back one step in the joint session history.

If there is no previous page, does nothing.

window . history . forward()

Goes forward one step in the joint session history.

If there is no next page, does nothing.

window . history . pushState(data, title [, url ] )

Pushes the given data onto the session history, with the given title, and, if provided, the given URL.

window . history . replaceState(data, title [, url ] )

Updates the current entry in the session histor to have the given data, title, and, if provided, URL.

The joint session history of a History object is the union of all the session histories of all browsing contexts of all the fully active Document objects that share the History object's top-level browsing context, with all the entries that are current entries in their respective session histories removed except for the current entry of the joint session history.

The current entry of the joint session history is the entry that most recently became a current entry in its session history.

Entries in the joint session history are ordered chronologically by the time they were added to their respective session histories. (Since all these browsing contexts by definition share an event loop, there is always a well-defined sequential order in which their session histories had their entries added.) Each entry has an index; the earliest entry has index 0, and the subsequent entries are numbered with consecutively increasing integers (1, 2, 3, etc).

The length attribute of the History interface must return the number of entries in the joint session history.

The actual entries are not accessible from script.

When the go(delta) method is invoked, if the argument to the method was omitted or has the value zero, the user agent must act as if the location.reload() method was called instead. Otherwise, the user agent must traverse the history by a delta whose value is the value of the method's argument.

When the back() method is invoked, the user agent must traverse the history by a delta −1.

When the forward()method is invoked, the user agent must traverse the history by a delta +1.

To traverse the history by a delta delta, the user agent must queue a task to run the following steps. The task source for the queued task is the history traversal task source.

Let delta be the argument to the method.
If the index of the current entry of the joint session history plus delta is less than zero or greater than or equal to the number of items in the joint session history, then the user agent must do nothing.
Let specified entry be the entry in the joint session history whose index is the sum of delta and the index of the current entry of the joint session history.
Let specified browsing context be the browsing context of the specified entry.
Traverse the history of the specified browsing context to the specified entry.

When the user navigates through a browsing context, e.g. using a browser's back and forward buttons, the user agent must traverse the history by a delta equivalent to the action specified by the user.

The pushState(data, title, url) method adds a state object entry to the history.

The replaceState(data, title, url) method updates the state object, title, and optionally the URL of the current entry in the history.

When either of these methods is invoked, the user agent must run the following steps:

Let clone data be a structured clone of the specified data. If this throws an exception, then rethrow that exception and abort these steps.
If a third argument is specified, run these substeps:
1. Resolve the value of the third argument, relative to the entry script's base URL.
2. If that fails, raise a SECURITY_ERR exception and abort these steps.
3. Compare the resulting absolute URL to the document's address. If any part of these two URLs differ other than the <path>, <query>, and <fragment> components, then raise a SECURITY_ERR exception and abort these steps.
4. If the origin of the resulting absolute URL is not the same as the origin of the entry script's document, and either the <path> or <query> components of the two URLs compared in the previous step differ, raise a SECURITY_ERR exception and abort these steps. (This prevents sandboxed content from spoofing other pages on the same origin.)
For the purposes of the comparisons in the above substeps, the <path> and <query> components can only be the same if the URLs use a hierarchical <scheme>.
If the method invoked was the pushState() method:
1. Remove all the entries in the browsing context's session history after the current entry. If the current entry is the last entry in the session history, then no entries are removed.
  
  This doesn't necessarily have to affect the user agent's user interface.
2. Remove any tasks queued by the history traversal task source.
3. Add a state object entry to the session history, after the current entry, with cloned data as the state object, the given title as the title, and, if the third argument is present, the absolute URL that was found earlier in this algorithm as the URL of the entry.
4. Update the current entry to be the this newly added entry.
Otherwise, if the method invoked was the replaceState() method:
1. Update the current entry in the session history so that cloned data is the entry's new state object, the given title is the new title, and, if the third argument is present, the absolute URL that was found earlier in this algorithm is the entry's new URL.
If the third argument is present, set the document's current address to the absolute URL that was found earlier in this algorithm.

Since this is neither a navigation of the browsing context nor a history traversal, it does not cause a hashchange event to be fired.

The title is purely advisory. User agents might use the title in the user interface.

User agents may limit the number of state objects added to the session history per page. If a page hits the UA-defined limit, user agents must remove the entry immediately after the first entry for that Document object in the session history after having added the new entry. (Thus the state history acts as a FIFO buffer for eviction, but as a LIFO buffer for navigation.)

Consider a game where the user can navigate along a line, such that the user is always at some coordinate, and such that the user can bookmark the page corresponding to a particular coordinate, to return to it later.

A static page implementing the x=5 position in such a game could look like the following:

<!DOCTYPE HTML>
<!-- this is http://example.com/line?x=5 -->
<title>Line Game - 5</title>
<p>You are at coordinate 5 on the line.</p>
<p>
 <a href="?x=6">Advance to 6</a> or
 <a href="?x=4">retreat to 4</a>?
</p>

The problem with such a system is that each time the user clicks, the whole page has to be reloaded. Here instead is another way of doing it, using script:

<!DOCTYPE HTML>
<!-- this starts off as http://example.com/line?x=5 -->
<title>Line Game - 5</title>
<p>You are at coordinate <span id="coord">5</span> on the line.</p>
<p>
 <a href="?x=6" onclick="go(1)">Advance to 6</a> or
 <a href="?x=4" onclick="go(-1)">retreat to 4</a>?
</p>
<script>
 var currentPage = 5; // prefilled by server
 function go(d) {
   history.pushState(currentPage, 'Line Game - ' + currentPage, '?x=' + currentPage);
   setupPage(currentPage + d);
 }
 onpopstate = function(event) {
   setupPage(event.state);
 }
 function setupPage(page) {
   currentPage = page;
   document.title = 'Line Game - ' + currentPage;
   document.getElementById('coord').textContent = currentPage;
   document.links[0].href = '?x=' + (currentPage+1);
   document.links[0].textContent = 'Advance to ' + (currentPage+1);
   document.links[1].href = '?x=' + (currentPage-1);
   document.links[1].textContent = 'retreat to ' + (currentPage-1);
 }
</script>

In systems without script, this still works like the previous example. However, users that do have script support can now navigate much faster, since there is no network access for the same experience. Furthermore, contrary to the experience the user would have with just a naïve script-based approach, bookmarking and navigating the session history still work.

In the example above, the data argument to the pushState() method is the same information as would be sent to the server, but in a more convenient form, so that the script doesn't have to parse the URL each time the user navigates.

Applications might not use the same title for a session history entry as the value of the document's title element at that time. For example, here is a simple page that shows a block in the title element. Clearly, when navigating backwards to a previous state the user does not go back in time, and therefore it would be inappropriate to put the time in the session history title.

<!DOCTYPE HTML> 
<TITLE>Line</TITLE>
<SCRIPT>
 setInterval(function () { document.title = 'Line - ' + new Date(); }, 1000);
 var i = 1;
 function inc() {
   set(i+1);
   history.pushState(i, 'Line - ' + i);
 }
 function set(newI) {
   i = newI;
   document.forms.F.I.value = newI;
 }
</SCRIPT>
<BODY ONPOPSTATE="recover(event.state)">
<FORM NAME=F>
State: <OUTPUT NAME=I>1</OUTPUT> <INPUT VALUE="Increment" TYPE=BUTTON ONCLICK="inc()">
</FORM>

5.4.3 The `Location` interface

Status: Last call for comments

Each Document object in a browsing context's session history is associated with a unique instance of a Location object.

document . location [ = value ]

window . location [ = value ]

Returns a Location object with the current page's location.

Can be set, to navigate to another page.

The location attribute of the HTMLDocument interface must return the Location object for that Document object, if it is in a browsing context, and null otherwise.

The location attribute of the Window interface must return the Location object for that Window object's Document.

Location objects provide a representation of their document's current address, and allow the current entry of the browsing context's session history to be changed, by adding or replacing entries in the history object.

interface Location {
  stringifier attribute DOMString href;
  void assign(in DOMString url);
  void replace(in DOMString url);
  void reload();

  // URL decomposition IDL attributes 
           attribute DOMString protocol;
           attribute DOMString host;
           attribute DOMString hostname;
           attribute DOMString port;
           attribute DOMString pathname;
           attribute DOMString search;
           attribute DOMString hash;

  // resolving relative URLs
  DOMString resolveURL(in DOMString url);
};

location . href [ = value ]

Returns the current page's location.

Can be set, to navigate to another page.

location . assign(url)

Navigates to the given page.

location . replace(url)

Removes the current page from the session history and navigates to the given page.

location . reload()

Reloads the current page.

url = location . resolveURL(url)

Resolves the given relative URL to an absolute URL.

The href attribute must return the current address of the associated Document object, as an absolute URL.

On setting, the user agent must act as if the assign() method had been called with the new value as its argument.

When the assign(url) method is invoked, the UA must resolve the argument, relative to the entry script's base URL, and if that is successful, must navigate the browsing context to the specified url. If the browsing context's session history contains only one Document, and that was the about:blank Document created when the browsing context was created, then the navigation must be done with replacement enabled.

When the replace(url) method is invoked, the UA must resolve the argument, relative to the entry script's base URL, and if that is successful, navigate the browsing context to the specified url with replacement enabled.

Navigation for the assign() and replace() methods must be done with the browsing context of the script that invoked the method as the source browsing context.

If the resolving step of the assign() and replace() methods is not successful, then the user agent must instead throw a SYNTAX_ERR exception.

When the reload() method is invoked, the user agent must run the appropriate steps from the following list:

If the currently executing task is the dispatch of a resize event in response to the user resizing the browsing context: Repaint the browsing context and abort these steps.
Otherwise: Navigate the browsing context to the document's current address with replacement enabled. The source browsing context must be the browsing context being navigated.

When a user requests that the current page be reloaded through a user interface element, the user agent should navigate the browsing context to the same resource as Document, with replacement enabled. In the case of non-idempotent methods (e.g. HTTP POST), the user agent should prompt the user to confirm the operation first, since otherwise transactions (e.g. purchases or database modifications) could be repeated. User agents may allow the user to explicitly override any caches when reloading.

The Location interface also has the complement of URL decomposition IDL attributes, protocol, host, port, hostname, pathname, search, and hash. These must follow the rules given for URL decomposition IDL attributes, with the input being the current address of the associated Document object, as an absolute URL (same as the href attribute), and the common setter action being the same as setting the href attribute to the new output value.

The resolveURL(url) method must resolve its url argument, relative to the entry script's base URL, and if that succeeds, return the resulting absolute URL. If it fails, it must throw a SYNTAX_ERR exception instead.

5.4.3.1 Security

Status: Last call for comments

User agents must raise a SECURITY_ERR exception whenever any of the members of a Location object are accessed by scripts whose effective script origin is not the same as the Location object's associated Document's effective script origin, with the following exceptions:

The href setter, if the script is running in a browsing context that is allowed to navigate the browsing context with which the Location object is associated
The replace() method, if the script is running in a browsing context that is allowed to navigate the browsing context with which the Location object is associated

5.4.4 Implementation notes for session history

Status: Last call for comments

This section is non-normative.

The History interface is not meant to place restrictions on how implementations represent the session history to the user.

For example, session history could be implemented in a tree-like manner, with each page having multiple "forward" pages. This specification doesn't define how the linear list of pages in the history object are derived from the actual session history as seen from the user's perspective.

Similarly, a page containing two iframes has a history object distinct from the iframes' history objects, despite the fact that typical Web browsers present the user with just one "Back" button, with a session history that interleaves the navigation of the two inner frames and the outer page.

Security: It is suggested that to avoid letting a page "hijack" the history navigation facilities of a UA by abusing pushState(), the UA provide the user with a way to jump back to the previous page (rather than just going back to the previous state). For example, the back button could have a drop down showing just the pages in the session history, and not showing any of the states. Similarly, an aural browser could have two "back" commands, one that goes back to the previous state, and one that jumps straight back to the previous page.

In addition, a user agent could ignore calls to pushState() that are invoked on a timer, or from event listeners that are not triggered in response to a clear user action, or that are invoked in rapid succession.

5.5 Browsing the Web

Status: Last call for comments

5.5.1 Navigating across documents

Status: Last call for comments

Certain actions cause the browsing context to navigate to a new resource. Navigation always involves source browsing context, which is the browsing context which was responsible for starting the navigation.

For example, following a hyperlink, form submission, and the window.open() and location.assign() methods can all cause a browsing context to navigate.

A user agent may provide various ways for the user to explicitly cause a browsing context to navigate, in addition to those defined in this specification.

When a browsing context is navigated to a new resource, the user agent must run the following steps:

Release the storage mutex.
If the source browsing context is not the same as the browsing context being navigated, and the source browsing context is not one of the ancestor browsing contexts of the browsing context being navigated, and the source browsing context had its sandboxed navigation browsing context flag set when its active document was created, then abort these steps. The user agent may offer to open the new resource in a new top-level browsing context or in the top-level browsing context of the source browsing context, at the user's option, in which case the user agent must navigate that designated top-level browsing context to the new resource as if the user had requested it independently.
If the source browsing context is the same as the browsing context being navigated, and this browsing context has its seamless browsing context flag set, then find the nearest ancestor browsing context that does not have its seamless browsing context flag set, and continue these steps as if that browsing context was the one that was going to be navigated instead.
If there is a preexisting attempt to navigate the browsing context, and the source browsing context is the same as the browsing context being navigated, and that attempt is currently running the unload a document algorithm, and the origin of the URL of the resource being loaded in that navigation is not the same origin as the origin of the URL of the resource being loaded in this navigation, then abort these steps without affecting the preexisting attempt to navigate the browsing context.
If there is a preexisting attempt to navigate the browsing context, and either that attempt has not yet matured (i.e. it has not passed the point of making its Document the active document), or that navigation's resource is not to be fetched using HTTP GET or equivalent, or its resource's absolute URL differs from this attempt's by more than the presence, absence, or value of the <fragment> component, then cancel that preexisting attempt to navigate the browsing context.
Fragment identifiers: If the absolute URL of the new resource is the same as the address of the active document of the browsing context being navigated, ignoring any <fragment> components of those URLs, and the new resource is to be fetched using HTTP GET or equivalent, and the absolute URL of the new resource has a <fragment> component (even if it is empty), then navigate to that fragment identifier and abort these steps.
Cancel any preexisting attempt to navigate the browsing context.
If the new resource is to be handled using a mechanism that does not affect the browsing context, e.g. ignoring the navigation request altogether because the specified scheme is not one of the supported protocols, then abort these steps and proceed with that mechanism instead.
Prompt to unload the Document object. If the user refused to allow the document to be unloaded, then these steps must be aborted.
If the new resource is to be handled by displaying some sort of inline content, e.g. an error message because the specified scheme is not one of the supported protocols, or an inline prompt to allow the user to select a registered handler for the given scheme, then display the inline content and abort these steps.

In the case of a registered handler being used, the algorithm will be reinvoked with a new URL to handle the request.
If the new resource is to be fetched using HTTP GET or equivalent, then check if there are any relevant application caches that are identified by a URL with the same origin as the URL in question, and that have this URL as one of their entries, excluding entries marked as foreign. If so, then the user agent must then get the resource from the most appropriate application cache of those that match.

For example, imagine an HTML page with an associated application cache displaying an image and a form, where the image is also used by several other application caches. If the user right-clicks on the image and chooses "View Image", then the user agent could decide to show the image from any of those caches, but it is likely that the most useful cache for the user would be the one that was used for the aforementioned HTML page. On the other hand, if the user submits the form, and the form does a POST submission, then the user agent will not use an application cache at all; the submission will be made to the network.

Otherwise, fetch the new resource, if it has not already been obtained.

If the resource is being fetched using a method other than one equivalent to HTTP's GET, or, if the navigation algorithm was invoked as a result of the form submission algorithm, then the fetching algorithm must be invoked from the origin of the active document of the source browsing context, if any.

If the browsing context being navigated is a child browsing context for an iframe or object element, then the fetching algorithm must be invoked from the iframe or object element's browsing context scope origin, if it has one.
At this point the user agents must return to whatever algorithm invoked the navigation steps and must continue these steps asynchronously.
If fetching the resource results in a redirect, return to the step labeled "fragment identifiers" with the new resource.
Wait for one or more bytes to be available or for the user agent to establish that the resource in question is empty. During this time, the user agent may allow the user to cancel this navigation attempt or start other navigation attempts.
If the resource was not fetched from an application cache, and was to be fetched using HTTP GET or equivalent, and its URL matches the fallback namespace of one or more relevant application caches, and the user didn't cancel the navigation attempt during the previous step, and the navigation attempt failed (e.g. the server returned a 4xx or 5xx status code or equivalent, or there was a DNS error), then:

Let candidate be the fallback resource specified for the fallback namespace in question. If multiple application caches match, the user agent must use the fallback of the most appropriate application cache of those that match.

If candidate is not marked as foreign, then the user agent must discard the failed load and instead continue along these steps using candidate as the resource. The document's address, if appropriate, will still be the originally requested URL, not the fallback URL, but the user agent may indicate to the user that the original page load failed, that the page used was a fallback resource, and what the URL of the fallback resource actually is.
If the document's out-of-band metadata (e.g. HTTP headers), not counting any type information (such as the Content-Type HTTP header), requires some sort of processing that will not affect the browsing context, then perform that processing and abort these steps.
Such processing might be triggered by, amongst other things, the following:
- HTTP status codes (e.g. 204 No Content or 205 Reset Content)
- HTTP Content-Disposition headers
- Network errors
HTTP 401 responses that do not include a challenge recognized by the user agent must be processed as if they had no challenge, e.g. rendering the entity body as if the response had been 200 OK.

User agents may show the entity body of an HTTP 401 response even when the response do include a recognized challenge, with the option to login being included in a non-modal fashion, to enable the information provided by the server to be used by the user before authenticating. Similarly, user agents should allow the user to authenticate (in a non-modal fashion) against authentication challenges included in other responses such as HTTP 200 OK responses, effectively allowing resources to present HTTP login forms without requiring their use.
Let type be the sniffed type of the resource.
If the user agent has been configured to process resources of the given type using some mechanism other than rendering the content in a browsing context, then skip this step. Otherwise, if the type is one of the following types, jump to the appropriate entry in the following list, and process the resource as described there:

"text/html"

"text/html-sandboxed"

Follow the steps given in the HTML document section, and abort these steps.

Any type ending in "+xml"

"application/xml"

"text/xml"

Follow the steps given in the XML document section. If that section determines that the content is not to be displayed as a generic XML document, then proceed to the next step in this overall set of steps. Otherwise, abort these steps.

"text/plain"

Follow the steps given in the plain text file section, and abort these steps.

A supported image type

Follow the steps given in the image section, and abort these steps.

A type that will use an external application to render the content in the browsing context

Follow the steps given in the plugin section, and abort these steps.

Setting the document's address: If there is no override URL, then any Document created by these steps must have its address set to the URL that was originally to be fetched, ignoring any other data that was used to obtain the resource (e.g. the entity body in the case of a POST submission is not part of the document's address, nor is the URL of the fallback resource in the case of the original load having failed and that URL having been found to match a fallback namespace). However, if there is an override URL, then any Document created by these steps must have its address set to that URL instead.

An override URL is set when dereferencing a javascript: URL.

Creating a new Document object: When a Document is created as part of the above steps, a new set of views along with the associated Window object must be created and associated with the Document, with one exception: if the browsing context's only entry in its session history is the about:blank Document that was added when the browsing context was created, and navigation is occurring with replacement enabled, and that Document has the same origin as the new Document, then the Window object and associated views of that Document must be used instead, and the document attribute of the AbstractView objects of those views must be changed to point to the new Document instead.
Non-document content: If, given type, the new resource is to be handled by displaying some sort of inline content, e.g. a native rendering of the content, an error message because the specified type is not supported, or an inline prompt to allow the user to select a registered handler for the given type, then display the inline content and abort these steps.

In the case of a registered handler being used, the algorithm will be reinvoked with a new URL to handle the request.
Otherwise, the document's type is such that the resource will not affect the browsing context, e.g. because the resource is to be handed to an external application. Process the resource appropriately.

Some of the sections below, to which the above algorithm defers in certain cases, require the user agent to update the session history with the new page. When a user agent is required to do this, it must queue a task to run the following steps:

Unload the Document object of the current entry, with the recycle parameter set to false.
If the navigation was initiated for entry update of an entry
1. Replace the Document of the entry being updated, and any other entries that referenced the same document as that entry, with the new Document.
2. Traverse the history to the new entry.
This can only happen if the entry being updated is no the current entry, and can never happen with replacement enabled. (It happens when the user tried to traverse to a session history entry that no longer had a Document object.)
Otherwise
1. Remove all the entries in the browsing context's session history after the current entry. If the current entry is the last entry in the session history, then no entries are removed.
  
  This doesn't necessarily have to affect the user agent's user interface.
2. Remove any tasks queued by the history traversal task source.
3. Append a new entry at the end of the History object representing the new resource and its Document object and related state.
4. Traverse the history to the new entry. If the navigation was initiated with replacement enabled, then the traversal must itself be initiated with replacement enabled.
The navigation algorithm has now matured.
Fragment identifier loop: Spin the event loop for a user-agent-defined amount of time, as desired by the user agent implementor. (This is intended to allow the user agent to optimize the user experience in the face of performance concerns.)
If the Document object has no parser, or its parser has stopped parsing, or the user agent has reason to believe the user is no longer interested in scrolling to the fragment identifier, then abort these steps.
Scroll to the fragment identifier given in the document's current address. If this fails to find an indicated part of the document, then return to the fragment identifier loop step.

The task source for this task is the networking task source.

5.5.2 Page load processing model for HTML files

Status: Last call for comments

When an HTML document is to be loaded in a browsing context, the user agent must queue a task to create a Document object, mark it as being an HTML document, create an HTML parser, and associate it with the document. Each task that the networking task source places on the task queue while the fetching algorithm runs must then fill the parser's input stream with the fetched bytes and cause the HTML parser to perform the appropriate processing of the input stream.

The input stream converts bytes into characters for use in the tokenizer. This process relies, in part, on character encoding information found in the real Content-Type metadata of the resource; the "sniffed type" is not used for this purpose.

When no more bytes are available, the user agent must queue a task for the parser to process the implied EOF character, which eventually causes a load event to be fired.

After creating the Document object, but before any script execution, certainly before the parser stops, the user agent must update the session history with the new page.

Application cache selection happens in the HTML parser.

The task source for the two tasks mentioned in this section must be the networking task source.

5.5.3 Page load processing model for XML files

Status: Last call for comments

When faced with displaying an XML file inline, user agents must first create a Document object, following the requirements of the XML and Namespaces in XML recommendations, RFC 3023, DOM3 Core, and other relevant specifications. [XML] [XMLNS] [RFC3023] [DOMCORE]

The actual HTTP headers and other metadata, not the headers as mutated or implied by the algorithms given in this specification, are the ones that must be used when determining the character encoding according to the rules given in the above specifications. Once the character encoding is established, the document's character encoding must be set to that character encoding.

If the root element, as parsed according to the XML specifications cited above, is found to be an html element with an attribute manifest, then, as soon as the element is inserted into the document, the user agent must resolve the value of that attribute relative to that element, and if that is successful, must run the application cache selection algorithm with the resulting absolute URL with any <fragment> component removed as the manifest URL, and passing in the newly-created Document. Otherwise, if the attribute is absent or resolving it fails, then as soon as the root element is inserted into the document, the user agent must run the application cache selection algorithm with no manifest, and passing in the Document.

Because the processing of the manifest attribute happens only once the root element is parsed, any URLs referenced by processing instructions before the root element (such as <?xml-stylesheet?> and <?xbl?> PIs) will be fetched from the network and cannot be cached.

User agents may examine the namespace of the root Element node of this Document object to perform namespace-based dispatch to alternative processing tools, e.g. determining that the content is actually a syndication feed and passing it to a feed handler. If such processing is to take place, abort the steps in this section, and jump to the next step (labeled "non-document content") in the navigate steps above.

Otherwise, then, with the newly created Document, the user agents must update the session history with the new page. User agents may do this before the complete document has been parsed (thus achieving incremental rendering), and must do this before any scripts are to be executed.

Error messages from the parse process (e.g. XML namespace well-formedness errors) may be reported inline by mutating the Document.

5.5.4 Page load processing model for text files

Status: Implemented and widely deployed

When a plain text document is to be loaded in a browsing context, the user agent should queue a task to create a Document object, mark it as being an HTML document, create an HTML parser, associate it with the document, act as if the tokenizer had emitted a start tag token with the tag name "pre" followed by a single U+000A LINE FEED (LF) character, and switch the HTML parser's tokenizer to the PLAINTEXT state. Each task that the networking task source places on the task queue while the fetching algorithm runs must then fill the parser's input stream with the fetched bytes and cause the HTML parser to perform the appropriate processing of the input stream.

The rules for how to convert the bytes of the plain text document into actual characters are defined in RFC 2046, RFC 2646, and subsequent versions thereof. [RFC2046] [RFC2646]

The document's character encoding must be set to the character encoding used to decode the document.

Upon creation of the Document object, the user agent must run the application cache selection algorithm with no manifest, and passing in the newly-created Document.

When no more bytes are available, the user agent must queue a task for the parser to process the implied EOF character, which eventually causes a load event to be fired.

After creating the Document object, but potentially before the page has finished parsing, the user agent must update the session history with the new page.

User agents may add content to the head element of the Document, e.g. linking to a style sheet or an XBL binding, providing script, giving the document a title, etc.

The task source for the two tasks mentioned in this section must be the networking task source.

5.5.5 Page load processing model for images

Status: Last call for comments

When an image resource is to be loaded in a browsing context, the user agent should create a Document object, mark it as being an HTML document, append an html element to the Document, append a head element and a body element to the html element, append an img to the body element, and set the src attribute of the img element to the address of the image.

Then, the user agent must act as if it had stopped parsing.

Upon creation of the Document object, the user agent must run the application cache selection algorithm with no manifest, and passing in the newly-created Document.

After creating the Document object, but potentially before the page has finished fully loading, the user agent must update the session history with the new page.

User agents may add content to the head element of the Document, or attributes to the img element, e.g. to link to a style sheet or an XBL binding, to provide a script, to give the document a title, etc.

5.5.6 Page load processing model for content that uses plugins

Status: Last call for comments

When a resource that requires an external resource to be rendered is to be loaded in a browsing context, the user agent should create a Document object, mark it as being an HTML document, append an html element to the Document, append a head element and a body element to the html element, append an embed to the body element, and set the src attribute of the embed element to the address of the resource.

Then, the user agent must act as if it had stopped parsing.

Upon creation of the Document object, the user agent must run the application cache selection algorithm with no manifest, and passing in the newly-created Document.

After creating the Document object, but potentially before the page has finished fully loading, the user agent must update the session history with the new page.

User agents may add content to the head element of the Document, or attributes to the embed element, e.g. to link to a style sheet or an XBL binding, or to give the document a title.

If the sandboxed plugins browsing context flag was set on the browsing context when the Document was created, the synthesized embed element will fail to render the content.

5.5.7 Page load processing model for inline content that doesn't have a DOM

Status: Last call for comments

When the user agent is to display a user agent page inline in a browsing context, the user agent should create a Document object, mark it as being an HTML document, and then either associate that Document with a custom rendering that is not rendered using the normal Document rendering rules, or mutate that Document until it represents the content the user agent wants to render.

Once the page has been set up, the user agent must act as if it had stopped parsing.

Upon creation of the Document object, the user agent must run the application cache selection algorithm with no manifest, passing in the newly-created Document.

After creating the Document object, but potentially before the page has been completely set up, the user agent must update the session history with the new page.

5.5.8 Navigating to a fragment identifier

Status: Last call for comments

When a user agent is supposed to navigate to a fragment identifier, then the user agent must queue a task to run the following steps:

Remove all the entries in the browsing context's session history after the current entry. If the current entry is the last entry in the session history, then no entries are removed.

This doesn't necessarily have to affect the user agent's user interface.
Remove any tasks queued by the history traversal task source.
Append a new entry at the end of the History object representing the new resource and its Document object and related state. Its URL must be set to the address to which the user agent was navigating. The title must be left unset.
Traverse the history to the new entry. This will scroll to the fragment identifier given in what is now the document's current address.

If the scrolling fails because the relevant ID has not yet been parsed, then the original navigation algorithm will take care of the scrolling instead, as the last few steps of its update the session history with the new page algorithm.

When the user agent is required to scroll to the fragment identifier, it must change the scrolling position of the document, or perform some other action, such that the indicated part of the document is brought to the user's attention. If there is no indicated part, then the user agent must not scroll anywhere.

The indicated part of the document is the one that the fragment identifier, if any, identifies. The semantics of the fragment identifier in terms of mapping it to a specific DOM Node is defined by the specification that defines the MIME type used by the Document (for example, the processing of fragment identifiers for XML MIME types is the responsibility of RFC3023). [RFC3023]

For HTML documents (and HTML MIME types), the following processing model must be followed to determine what the indicated part of the document is.

Parse the URL, and let fragid be the <fragment> component of the URL.
If fragid is the empty string, then the indicated part of the document is the top of the document; stop the algorithm here.
Let decoded fragid be the result of expanding any sequences of percent-encoded octets in fragid that are valid UTF-8 sequences into Unicode characters as defined by UTF-8. If any percent-encoded octets in that string are not valid UTF-8 sequences, then skip this step and the next one.
If this step was not skipped and there is an element in the DOM that has an ID exactly equal to decoded fragid, then the first such element in tree order is the indicated part of the document; stop the algorithm here.
If there is an a element in the DOM that has a name attribute whose value is exactly equal to fragid (not decoded fragid), then the first such element in tree order is the indicated part of the document; stop the algorithm here.
If fragid is an ASCII case-insensitive match for the string top, then the indicated part of the document is the top of the document; stop the algorithm here.
Otherwise, there is no indicated part of the document.

For the purposes of the interaction of HTML with Selectors' :target pseudo-class, the target element is the indicated part of the document, if that is an element; otherwise there is no target element. [SELECTORS]

5.5.9 History traversal

Status: Last call for comments

When a user agent is required to traverse the history to a specified entry, optionally with replacement enabled, the user agent must act as follows:

If there is no longer a Document object for the entry in question, the user agent must navigate the browsing context to the location for that entry to perform an entry update of that entry, and abort these steps. The "navigate" algorithm reinvokes this "traverse" algorithm to complete the traversal, at which point there is a Document object and so this step gets skipped. The navigation must be done using the same source browsing context as was used the first time this entry was created. (This can never happen with replacement enabled.)
If the current entry's title was not set by the pushState() or replaceState() methods, then set its title to the value returned by the document.title IDL attribute.
If appropriate, update the current entry in the browsing context's Document object's History object to reflect any state that the user agent wishes to persist. The entry is then said to be an entry with persisted user state.

For example, some user agents might want to persist the scroll position, or the values of form controls.
If the specified entry has a different Document object than the current entry then the user agent must run the following substeps:
1. If the browsing context is a top-level browsing context, but not an auxiliary browsing context, and the origin of the Document of the specified entry is not the same as the origin of the Document of the current entry, then the following sub-sub-steps must be run:
  1. The current browsing context name must be stored with all the entries in the history that are associated with Document objects with the same origin as the active document and that are contiguous with the current entry.
  2. The browsing context's browsing context name must be unset.
2. The user agent must make the specified entry's Document object the active document of the browsing context.
3. If the specified entry has a browsing context name stored with it, then the following sub-sub-steps must be run:
  1. The browsing context's browsing context name must be set to the name stored with the specified entry.
  2. Any browsing context name stored with the entries in the history that are associated with Document objects with the same origin as the new active document, and that are contiguous with the specified entry, must be cleared.
4. If the specified entry's Document has any input elements whose resulting autocompletion state is off, invoke the reset algorithm of each of those elements.
5. If the current document readiness of the specified entry's Document is "complete", queue a task to fire a pageshow event at the Window object of that Document, but with its target set to the Document object (and the currentTarget set to the Window object), using the PageTransitionEvent interface, with the persisted attribute set to true. This event must not bubble, must not be cancelable, and has no default action.
Set the document's current address to the URL of the specified entry.
If the specified entry has a URL that differs from the current entry's only by its fragment identifier, and the two share the same Document object, then let hash changed be true, and let old URL be the URL of the current entry and new URL be the URL of the specified entry. Otherwise, let hash changed be false.
If the traversal was initiated with replacement enabled, remove the entry immediately before the specified entry in the session history.
If hash changed is true, then, if the new URL has a fragment identifier, scroll to the fragment identifier.
If the entry is an entry with persisted user state, the user agent may update aspects of the document view, for instance the scroll position or values of form fields, that it had previously recorded.
If the specified entry is a state object or the first entry for a Document, the user agent must run the following substeps:
1. If the entry is a state object entry, let state be a structured clone of that state object. Otherwise, let state be null.
2. Run the appropriate steps according to the conditions described:
  
  If the current document readiness is set to the string "complete"
  
  Queue a task to fire a popstate event at the Window object of the Document, using the PopStateEvent interface, with the state attribute set to the value of state. This event must bubble but not be cancelable and has no default action.
  
  Otherwise
  
  Let the Document's pending state object be state. (If there was already a pending state object, the previous one is discarded.)
  
  The event will then be fired just after the load event.
If hash changed is true, then queue a task to fire a hashchange event at the browsing context's Window object, using the HashChangeEvent interface, with the oldURL attribute set to old URL and the newURL attribute set to new URL. This event must bubble but not be cancelable and has no default action.
The current entry is now the specified entry.

The pending state object must be initially null.

The task source for the tasks mentioned above is the DOM manipulation task source.

5.5.9.1 Event definitions

Status: Last call for comments

The popstate event is fired when navigating to a session history entry that represents a state object.

interface PopStateEvent : Event {
  readonly attribute any state;
  void initPopStateEvent(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in any stateArg);
};

event . state: Returns a copy of the information that was provided to pushState() or replaceState().

The initPopStateEvent() method must initialize the event in a manner analogous to the similarly-named method in the DOM Events interfaces. [DOMEVENTS]

The state attribute represents the context information for the event, or null, if the state represented is the initial state of the Document.

The hashchange event is fired when navigating to a session history entry whose URL differs from that of the previous one only in the fragment identifier.

interface HashChangeEvent : Event {
  readonly attribute any oldURL;
  readonly attribute any newURL;
  void initHashChangeEvent(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in DOMString oldURLArg, in DOMString newURLArg);
};

event . oldURL: Returns the URL of the session history entry that was previously current.
event . newURL: Returns the URL of the session history entry that is now current.

The initHashChangeEvent() method must initialize the event in a manner analogous to the similarly-named method in the DOM Events interfaces. [DOMEVENTS]

The oldURL attribute represents context information for the event, specifically the URL of the session history entry that was traversed from.

The newURL attribute represents context information for the event, specifically the URL of the session history entry that was traversed to.

The pageshow event is fired when traversing to a session history entry.

The pagehide event is fired when traversing from a session history entry.

interface PageTransitionEvent : Event {
  readonly attribute any persisted;
  void initPageTransitionEvent(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in any persistedArg);
};

event . persisted: Returns false if the page is newly being loaded (and the load event will fire). Otherwise, returns true.

The initPageTransitionEvent() method must initialize the event in a manner analogous to the similarly-named method in the DOM Events interfaces. [DOMEVENTS]

The persisted attribute represents the context information for the event.

5.5.10 Unloading documents

Status: Last call for comments

A Document has a salvageable state, which is initially true.

When a user agent is to prompt to unload a document, it must run the following steps.

Let event be a new BeforeUnloadEvent event object with the name beforeunload, which does not bubble but is cancelable.
Dispatch: Dispatch event at the Document's Window object.
Release the storage mutex.
If any event listeners were triggered by the earlier dispatch step, then set the Document's salvageable state to false.
If the returnValue attribute of the event object is not the empty string, or if the event was canceled, then the user agent should ask the user to confirm that they wish to unload the document.

The prompt shown by the user agent may include the string of the returnValue attribute, or some leading subset thereof. (A user agent may want to truncate the string to 1024 characters for display, for instance.)

The user agent must pause while waiting for the user's response.

If the user did not confirm the page navigation, then the user agent refused to allow the document to be unloaded.
If this algorithm was invoked by another instance of the "prompt to unload a document" algorithm (i.e. through the steps below that invoke this algorithm for all descendant browsing contexts), then abort these steps here.
Let descendants be the list of the descendant browsing contexts of the Document.
If descendants is not an empty list, then for each browsing context b in descendants run the following substeps:
1. Prompt to unload the active document of the browsing context b. If the user refused to allow the document to be unloaded, then the user implicitly also refused to allow this document to be unloaded; abort these steps.
2. If salvageable state of the active document of the browsing context b is false, then set the salvageable state of this document to false also.

When a user agent is to unload a document, it must run the following steps. These steps are passed an argument, recycle, which is either true or false, indicating whether the Document object is going to be re-used. (This is set by the document.open() method.)

Fire a pagehide event at the Window object of the Document, but with its target set to the Document object (and the currentTarget set to the Window object), using the PageTransitionEvent interface, with the persisted attribute set to true. This event must not bubble, must not be cancelable, and has no default action.
Unload event: Fire a simple event named unload at the Document's Window object.
Release the storage mutex.
If any event listeners were triggered by the earlier unload event step, then set the Document object's salvageable state to false.
Run any unloading document cleanup steps for Document that are defined by this specification or any other relevant specifications.
If this algorithm was invoked by another instance of the "unload a document" algorithm (i.e. through the steps below that invoke this algorithm for all descendant browsing contexts), then abort these steps here.
Let descendants be the list of the descendant browsing contexts of the Document.
If descendants is not an empty list, then for each browsing context b in descendants run the following substeps:
1. Unload the active document of the browsing context b with the recycle parameter set to false.
2. If salvageable state of the active document of the browsing context b is false, then set the salvageable state of this document to false also.
If salvageable and recycle are both false, then the Document's browsing context must discard the Document.

This specification defines the following unloading document cleanup steps. Other specifications can define more.

If there are any outstanding transactions that have callbacks that involve scripts whose global object is the Document's Window object, roll them back (without invoking any of the callbacks) and set the Document's salvageable state to false. [WEBSQL]
Close the WebSocket connection of any WebSocket objects that were created by the WebSocket() constructor visible on the Document's Window object. If this affected any WebSocket objects, the set Document's salvageable state to false. [WEBSOCKET]
If the Document's salvageable state is false, empty the Document's Window's list of active timeouts and its list of active intervals.

5.5.10.1 Event definition

Status: Last call for comments

interface BeforeUnloadEvent : Event {
           attribute DOMString returnValue;
};

event . returnValue [ = value ]

Returns the current return value of the event (the message to show the user).

Can be set, to update the message.

There are no BeforeUnloadEvent-specific initialization methods.

The returnValue attribute represents the message to show the user. When the event is created, the attribute must be set to the empty string. On getting, it must return the last value it was set to. On setting, the attribute must be set to the new value.

5.5.11 Aborting a document load

Status: Last call for comments

If the user cancels any instance of the fetching algorithm in the context of a Document in a browsing context, then, if that Document is an active document, the user agent must queue a task to fire a simple event named abort at that Document's Window object.

5.6 Offline Web applications

Status: Last call for comments

5.6.1 Introduction

Status: Last call for comments

This section is non-normative.

In order to enable users to continue interacting with Web applications and documents even when their network connection is unavailable — for instance, because they are traveling outside of their ISP's coverage area — authors can provide a manifest which lists the files that are needed for the Web application to work offline and which causes the user's browser to keep a copy of the files for use offline.

To illustrate this, consider a simple clock applet consisting of an HTML page "clock.html", a CSS style sheet "clock.css", and a JavaScript script "clock.js".

Before adding the manifest, these three files might look like this:

<!-- clock.html -->
<!DOCTYPE HTML>
<html>
 <head>
  <title>Clock</title>
  <script src="clock.js"></script>
  <link rel="stylesheet" href="clock.css">
 </head>
 <body>
  <p>The time is: <output id="clock"></output></p>
 </body>
</html>

/* clock.css */
output { font: 2em sans-serif; }

/* clock.js */
setTimeout(function () {
    document.getElementById('clock').value = new Date();
}, 1000);

If the user tries to open the "clock.html" page while offline, though, the user agent (unless it happens to have it still in the local cache) will fail with an error.

The author can instead provide a manifest of the three files:

CACHE MANIFEST
clock.html
clock.css
clock.js

With a small change to the HTML file, the manifest (served as text/cache-manifest) is linked to the application:

<!-- clock.html -->
<!DOCTYPE HTML>
<html manifest="clock.manifest">
 <head>
  <title>Clock</title>
  <script src="clock.js"></script>
  <link rel="stylesheet" href="clock.css">
 </head>
 <body>
  <p>The time is: <output id="clock"></output></p>
 </body>
</html>

Now, if the user goes to the page, the browser will cache the files and make them available even when the user is offline.

Authors are encouraged to include the main page in the manifest also, but in practice the page that referenced the manifest is automatically cached even if it isn't explicitly mentioned.

HTTP cache headers and restrictions on caching pages served over TLS (encrypted, using https:) are overridden by manifests. Thus, pages will not expire from an application cache before the user agent has updated it, and even applications served over TLS can be made to work offline.

5.6.1.1 Event summary

Status: Last call for comments

This section is non-normative.

When the user visits a page that declares a manifest, the browser will try to update the cache. It does this by fetching a copy of the manifest and, if the manifest has changed since the user agent last saw it, redownloading all the resources it mentions and caching them anew.

As this is going on, a number of events get fired on the ApplicationCache object to keep the script updated as to the state of the cache update, so that the user can be notified appropriately. The events are as follows:

Event name	Interface	Dispatched when...	Next events
`checking`	`Event`	The user agent is checking for an update, or attempting to download the manifest for the first time. This is always the first event in the sequence.	`noupdate`, `downloading`, `obsolete`, `error`
`noupdate`	`Event`	The manifest hadn't changed.	Last event in sequence.
`downloading`	`Event`	The user agent has found an update and is fetching it, or is downloading the resources listed by the manifest for the first time.	`progress`, `error`, `cached`, `updateready`
`progress`	`ProgressEvent`	The user agent is downloading resources listed by the manifest.	`progress`, `error`, `cached`, `updateready`
`cached`	`Event`	The resources listed in the manifest have been downloaded, and the application is now cached.	Last event in sequence.
`updateready`	`Event`	The resources listed in the manifest have been newly redownloaded, and the script can use `swapCache()` to switch to the new cache.	Last event in sequence.
`obsolete`	`Event`	The manifest was found to have become a 404 or 410 page, so the application cache is being deleted.	Last event in sequence.
`error`	`Event`	The manifest was a 404 or 410 page, so the attempt to cache the application has been aborted.	Last event in sequence.
		The manifest hadn't changed, but the page referencing the manifest failed to download properly.
		A fatal error occurred while fetching the resources listed in the manifest.
		The manifest changed while the update was being run.	The user agent will try fetching the files again momentarily.

5.6.2 Application caches

Status: Last call for comments

An application cache is a set of cached resources consisting of:

One or more resources (including their out-of-band metadata, such as HTTP headers, if any), identified by URLs, each falling into one (or more) of the following categories:

Master entries
Documents that were added to the cache because a browsing context was navigated to that document and the document indicated that this was its cache, using the manifest attribute.
The manifest
The resource corresponding to the URL that was given in a master entry's html element's manifest attribute. The manifest is fetched and processed during the application cache download process. All the master entries have the same origin as the manifest.
Explicit entries
Resources that were listed in the cache's manifest in an explicit section. Explicit entries can also be marked as foreign, which means that they have a manifest attribute but that it doesn't point at this cache's manifest.
Fallback entries
Resources that were listed in the cache's manifest in a fallback section.
A URL in the list can be flagged with multiple different types, and thus an entry can end up being categorized as multiple entries. For example, an entry can be a manifest entry and an explicit entry at the same time, if the manifest is listed within the manifest.
Zero or more fallback namespaces: URLs, used as prefix match patterns, each of which is mapped to a fallback entry. Each namespace URL has the same origin as the manifest.
Zero or more URLs that form the online whitelist namespaces.
An online whitelist wildcard flag, which is either open or blocking.

Each application cache has a completeness flag, which is either complete or incomplete.

An application cache group is a group of application caches, identified by the absolute URL of a resource manifest which is used to populate the caches in the group.

An application cache is newer than another if it was created after the other (in other words, application caches in an application cache group have a chronological order).

Only the newest application cache in an application cache group can have its completeness flag set to incomplete; the others are always all complete.

Each application cache group has an update status, which is one of the following: idle, checking, downloading.

A relevant application cache is an application cache that is the newest in its group to be complete.

Each application cache group has a list of pending master entries. Each entry in this list consists of a resource and a corresponding Document object. It is used during the application cache download process to ensure that new master entries are cached even if the application cache download process was already running for their application cache group when they were loaded.

An application cache group can be marked as obsolete, meaning that it must be ignored when looking at what application cache groups exist.

A cache host is a Document or a SharedWorkerGlobalScope object. A cache host can be associated with an application cache. [WEBWORKERS]

A Document initially is not associated with an application cache, but can become associated with one early during the page load process, when steps in the parser and in the navigation sections cause cache selection to occur.

A SharedWorkerGlobalScope can be associated with an application cache when it is created. [WEBWORKERS]

Each cache host has an associated ApplicationCache object.

Multiple application caches in different application cache groups can contain the same resource, e.g. if the manifests all reference that resource. If the user agent is to select an application cache from a list of relevant application caches that contain a resource, the user agent must use the application cache that the user most likely wants to see the resource from, taking into account the following:

which application cache was most recently updated,
which application cache was being used to display the resource from which the user decided to look at the new resource, and
which application cache the user prefers.

A URL matches a fallback namespace if there exists a relevant application cache whose manifest's URL has the same origin as the URL in question, and that has a fallback namespace that is a prefix match for the URL being examined. If multiple fallback namespaces match the same URL, the longest one is the one that matches. A URL looking for a fallback namespace can match more than one application cache at a time, but only matches one namespace in each cache.

If a manifest http://example.com/app1/manifest declares that http://example.com/resources/images is a fallback namespace, and the user navigates to HTTP://EXAMPLE.COM:80/resources/images/cat.png, then the user agent will decide that the application cache identified by http://example.com/app1/manifest contains a namespace with a match for that URL.

5.6.3 The cache manifest syntax

Status: Last call for comments

5.6.3.1 A sample manifest

Status: Last call for comments

This section is non-normative.

This example manifest requires two images and a style sheet to be cached and whitelists a CGI script.

CACHE MANIFEST
# the above line is required

# this is a comment
# there can be as many of these anywhere in the file
# they are all ignored
  # comments can have spaces before them
  # but must be alone on the line

# blank lines are ignored too

# these are files that need to be cached they can either be listed
# first, or a "CACHE:" header could be put before them, as is done
# lower down.
images/sound-icon.png
images/background.png
# note that each file has to be put on its own line

# here is a file for the online whitelist -- it isn't cached, and
# references to this file will bypass the cache, always hitting the
# network (or trying to, if the user is offline).
NETWORK:
comm.cgi

# here is another set of files to cache, this time just the CSS file.
CACHE:
style/default.css

It could equally well be written as follows:

CACHE MANIFEST
NETWORK:
comm.cgi
CACHE:
style/default.css
images/sound-icon.png
images/background.png

The following manifest defines a catch-all error page that is displayed for any page on the site while the user is offline. It also specifies that the online whitelist wildcard flag is open, meaning that accesses to resources on other sites will not be blocked. (Resources on the same site are already not blocked because of the catch-all fallback namespace.)

So long as all pages on the site reference this manifest, they will get cached locally as they are fetched, so that subsequent hits to the same page will load the page immediately from the cache. Until the manifest is changed, those pages will not be fetched from the server again. When the manifest changes, then all the files will be redownloaded.

Subresources, such as style sheets, images, etc, would only be cached using the regular HTTP caching semantics, however.

CACHE MANIFEST
FALLBACK:
/ /offline.html
NETWORK:
*

5.6.3.2 Writing cache manifests

Status: Last call for comments

Manifests must be served using the text/cache-manifest MIME type. All resources served using the text/cache-manifest MIME type must follow the syntax of application cache manifests, as described in this section.

An application cache manifest is a text file, whose text is encoded using UTF-8. Data in application cache manifests is line-based. Newlines must be represented by U+000A LINE FEED (LF) characters, U+000D CARRIAGE RETURN (CR) characters, or U+000D CARRIAGE RETURN (CR) U+000A LINE FEED (LF) pairs.

This is a willful violation of two aspects of RFC 2046, which requires all text/* types to support an open-ended set of character encodings and only allows CRLF line breaks. These requirements, however, are outdated; UTF-8 is now widely used, such that supporting other encodings is no longer necessary, and use of CR, LF, and CRLF line breaks is commonly supported and indeed sometimes CRLF is not supported by text editors. [RFC2046]

The first line of an application cache manifest must consist of the string "CACHE", a single U+0020 SPACE character, the string "MANIFEST", and either a U+0020 SPACE character, a U+0009 CHARACTER TABULATION (tab) character, a U+000A LINE FEED (LF) character, or a U+000D CARRIAGE RETURN (CR) character. The first line may optionally be preceded by a U+FEFF BYTE ORDER MARK (BOM) character. If any other text is found on the first line, it is ignored.

Subsequent lines, if any, must all be one of the following:

A blank line

Blank lines must consist of zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters only.

A comment

Comment lines must consist of zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters, followed by a single U+0023 NUMBER SIGN character (#), followed by zero or more characters other than U+000A LINE FEED (LF) and U+000D CARRIAGE RETURN (CR) characters.

Comments must be on a line on their own. If they were to be included on a line with a URL, the "#" would be mistaken for part of a fragment identifier.

A section header

Section headers change the current section. There are three possible section headers:

CACHE:: Switches to the explicit section.
FALLBACK:: Switches to the fallback section.
NETWORK:: Switches to the online whitelist section.

Section header lines must consist of zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters, followed by one of the names above (including the U+003A COLON character (:)) followed by zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters.

Ironically, by default, the current section is the explicit section.

Data for the current section

The format that data lines must take depends on the current section.

When the current section is the explicit section, data lines must consist of zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters, a valid URL identifying a resource other than the manifest itself, and then zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters.

When the current section is the fallback section, data lines must consist of zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters, a valid URL identifying a resource other than the manifest itself, one or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters, another valid URL identifying a resource other than the manifest itself, and then zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters.

When the current section is the online whitelist section, data lines must consist of zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters, either a single U+002A ASTERISK character (*) or a valid URL identifying a resource other than the manifest itself, and then zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters.

Manifests may contain sections more than once. Sections may be empty.

If the manifest's <scheme> is https: or another scheme intended for encrypted data transfer, then all URLs in explicit sections must have the same origin as the manifest itself.

URLs that are to be fallback pages associated with fallback namespaces, and those namespaces themselves, must be given in fallback sections, with the namespace being the first URL of the data line, and the corresponding fallback page being the second URL. All the other pages to be cached must be listed in explicit sections.

Fallback namespaces and fallback entries must have the same origin as the manifest itself.

A fallback namespace must not be listed more than once.

Namespaces that the user agent is to put into the online whitelist must all be specified in online whitelist sections. (This is needed for any URL that the page is intending to use to communicate back to the server.) To specify that all URLs are automatically whitelisted in this way, a U+002A ASTERISK character character (*) may be specified as one of the URLs.

Authors should not include namespaces in the online whitelist for which another namespace in the online whitelist is a prefix match.

Relative URLs must be given relative to the manifest's own URL. All URLs in the manifest must have the same <scheme> as the manifest itself (either explicitly or implicitly, through the use of relative URLs).

URLs in manifests must not have fragment identifiers (i.e. the U+0023 NUMBER SIGN character isn't allowed in URLs in manifests).

Fallback namespaces and namespaces in the online whitelist are matched by prefix match.

5.6.3.3 Parsing cache manifests

Status: Last call for comments

When a user agent is to parse a manifest, it means that the user agent must run the following steps:

The user agent must decode the byte stream corresponding with the manifest to be parsed, treating it as UTF-8. Bytes or sequences of bytes that are not valid UTF-8 sequences must be interpreted as a U+FFFD REPLACEMENT CHARACTER.
Let base URL be the absolute URL representing the manifest.
Let explicit URLs be an initially empty list of absolute URLs for explicit entries.
Let fallback URLs be an initially empty mapping of fallback namespaces to absolute URLs for fallback entries.
Let online whitelist namespaces be an initially empty list of absolute URLs for an online whitelist.
Let online whitelist wildcard flag be blocking.
Let input be the decoded text of the manifest's byte stream.
Let position be a pointer into input, initially pointing at the first character.
If position is pointing at a U+FEFF BYTE ORDER MARK (BOM) character, then advance position to the next character.
If the characters starting from position are "CACHE", followed by a U+0020 SPACE character, followed by "MANIFEST", then advance position to the next character after those. Otherwise, this isn't a cache manifest; abort this algorithm with a failure while checking for the magic signature.
If the character at position is neither a U+0020 SPACE character, a U+0009 CHARACTER TABULATION (tab) character, U+000A LINE FEED (LF) character, nor a U+000D CARRIAGE RETURN (CR) character, then this isn't a cache manifest; abort this algorithm with a failure while checking for the magic signature.
This is a cache manifest. The algorithm cannot fail beyond this point (though bogus lines can get ignored).
Collect a sequence of characters that are not U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters, and ignore those characters. (Extra text on the first line, after the signature, is ignored.)
Let mode be "explicit".
Start of line: If position is past the end of input, then jump to the last step. Otherwise, collect a sequence of characters that are U+000A LINE FEED (LF), U+000D CARRIAGE RETURN (CR), U+0020 SPACE, or U+0009 CHARACTER TABULATION (tab) characters.
Now, collect a sequence of characters that are not U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters, and let the result be line.
Drop any trailing U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters at the end of line.
If line is the empty string, then jump back to the step labeled "start of line".
If the first character in line is a U+0023 NUMBER SIGN character (#), then jump back to the step labeled "start of line".
If line equals "CACHE:" (the word "CACHE" followed by a U+003A COLON character (:)), then set mode to "explicit" and jump back to the step labeled "start of line".
If line equals "FALLBACK:" (the word "FALLBACK" followed by a U+003A COLON character (:)), then set mode to "fallback" and jump back to the step labeled "start of line".
If line equals "NETWORK:" (the word "NETWORK" followed by a U+003A COLON character (:)), then set mode to "online whitelist" and jump back to the step labeled "start of line".
If line ends with a U+003A COLON character (:), then set mode to "unknown" and jump back to the step labeled "start of line".
This is either a data line or it is syntactically incorrect.
Let position be a pointer into line, initially pointing at the start of the string.
Let tokens be a list of strings, initially empty.
While position doesn't point past the end of line:
1. Let current token be an empty string.
2. While position doesn't point past the end of line and the character at position is neither a U+0020 SPACE nor a U+0009 CHARACTER TABULATION (tab) character, add the character at position to current token and advance position to the next character in input.
3. Add current token to the tokens list.
4. While position doesn't point past the end of line and the character at position is either a U+0020 SPACE or a U+0009 CHARACTER TABULATION (tab) character, advance position to the next character in input.
Process tokens as follows:

If mode is "explicit"

Resolve the first item in tokens, relative to base URL; ignore the rest.

If this fails, then jump back to the step labeled "start of line".

If the resulting absolute URL has a different <scheme> component than the manifest's URL (compared in an ASCII case-insensitive manner), then jump back to the step labeled "start of line". If the manifest's <scheme> is https: or another scheme intended for encrypted data transfer, and the resulting absolute URL does not have the same origin as the manifest's URL, then jump back to the step labeled "start of line".

Drop the <fragment> component of the resulting absolute URL, if it has one.

Add the resulting absolute URL to the explicit URLs.

If mode is "fallback"

Let part one be the first token in tokens, and let part two be the second token in tokens.

Resolve part one and part two, relative to base URL.

If either fails, then jump back to the step labeled "start of line".

If the absolute URL corresponding to either part one or part two does not have the same origin as the manifest's URL, then jump back to the step labeled "start of line".

Drop any the <fragment> components of the resulting absolute URLs.

If the absolute URL corresponding to part one is already in the fallback URLs mapping as a fallback namespace, then jump back to the step labeled "start of line".

Otherwise, add the absolute URL corresponding to part one to the fallback URLs mapping as a fallback namespace, mapped to the absolute URL corresponding to part two as the fallback entry.

If mode is "online whitelist"

If the first item in tokens is a U+002A ASTERISK character (*), then set online whitelist wildcard flag to open and jump back to the step labeled "start of line".

Otherwise, resolve the first item in tokens, relative to base URL; ignore the rest.

If this fails, then jump back to the step labeled "start of line".

If the resulting absolute URL has a different <scheme> component than the manifest's URL (compared in an ASCII case-insensitive manner), then jump back to the step labeled "start of line".

Drop the <fragment> component of the resulting absolute URL, if it has one.

Add the resulting absolute URL to the online whitelist namespaces.

If mode is "unknown"

Do nothing. The line is ignored.
Jump back to the step labeled "start of line". (That step jumps to the next, and last, step when the end of the file is reached.)
Return the explicit URLs list, the fallback URLs mapping, the online whitelist namespaces, and the online whitelist wildcard flag.

If a resource is listed in the explicit section or as a fallback entry in the fallback section, the resource will always be taken from the cache, regardless of any other matching entries in the fallback namespaces or online whitelist namespaces.

When a fallback namespace and an online whitelist namespace overlap, the online whitelist namespace has priority.

The online whitelist wildcard flag is applied last, only for URLs that match neither the online whitelist namespace nor the fallback namespace and that are not listed in the explicit section.

5.6.4 Downloading or updating an application cache

Status: Last call for comments

When the user agent is required (by other parts of this specification) to start the application cache download process for an absolute URL purported to identify a manifest, or for an application cache group, potentially given a particular cache host, and potentially given a master resource, the user agent must run the steps below. These steps are always run asynchronously, in parallel with the event loop tasks.

Some of these steps have requirements that only apply if the user agent shows caching progress. Support for this is optional. Caching progress UI could consist of a progress bar or message panel in the user agent's interface, or an overlay, or something else. Certain events fired during the application cache download process allow the script to override the display of such an interface. The goal of this is to allow Web applications to provide more seamless update mechanisms, hiding from the user the mechanics of the application cache mechanism. User agents may display user interfaces independent of this, but are encouraged to not show prominent update progress notifications for applications that cancel the relevant events.

These events are delayed until after the load event has fired.

The application cache download process steps are as follows:

Optionally, wait until the permission to start the application cache download process has been obtained from the user and until the user agent is confident that the network is available. This could include doing nothing until the user explicitly opts-in to caching the site, or could involve prompting the user for permission. The algorithm might never get past this point. (This step is particularly intended to be used by user agents running on severely space-constrained devices or in highly privacy-sensitive environments).
Atomically, so as to avoid race conditions, perform the following substeps:
1. Pick the appropriate substeps:
  
  If these steps were invoked with an absolute URL purported to identify a manifest
  
  Let manifest URL be that absolute URL.
  
  If there is no application cache group identified by manifest URL, then create a new application cache group identified by manifest URL. Initially, it has no application caches. One will be created later in this algorithm.
  
  If these steps were invoked with an application cache group
  
  Let manifest URL be the absolute URL of the manifest used to identify the application cache group to be updated.
2. Let cache group be the application cache group identified by manifest URL.
3. If these steps were invoked with a master resource, then add the resource, along with the resource's Document, to cache group's list of pending master entries.
4. If these steps were invoked with a cache host, and the status of cache group is checking or downloading, then queue a post-load task to fire a simple event named checking that is cancelable at the ApplicationCache singleton of that cache host. The default action of this event must be, if the user agent shows caching progress, the display of some sort of user interface indicating to the user that the user agent is checking to see if it can download the application.
5. If these steps were invoked with a cache host, and the status of cache group is downloading, then also queue a post-load task to fire a simple event named downloading that is cancelable at the ApplicationCache singleton of that cache host. The default action of this event must be, if the user agent shows caching progress, the display of some sort of user interface indicating to the user the application is being downloaded.
6. If the status of the cache group is either checking or downloading, then abort this instance of the application cache download process, as an update is already in progress.
7. Set the status of cache group to checking.
8. For each cache host associated with an application cache in cache group, queue a post-load task to fire a simple event that is cancelable named checking at the ApplicationCache singleton of the cache host. The default action of these events must be, if the user agent shows caching progress, the display of some sort of user interface indicating to the user that the user agent is checking for the availability of updates.
The remainder of the steps run asynchronously.

If cache group already has an application cache in it, then this is an upgrade attempt. Otherwise, this is a cache attempt.
If this is a cache attempt, then this algorithm was invoked with a cache host; queue a post-load task to fire a simple event named checking that is cancelable at the ApplicationCache singleton of that cache host. The default action of this event must be, if the user agent shows caching progress, the display of some sort of user interface indicating to the user that the user agent is checking for the availability of updates.
Fetching the manifest: Fetch the resource from manifest URL, and let manifest be that resource.

If the resource is labeled with the MIME type text/cache-manifest, parse manifest according to the rules for parsing manifests, obtaining a list of explicit entries, fallback entries and the fallback namespaces that map to them, entries for the online whitelist, and a value for the online whitelist wildcard flag.
If fetching the manifest fails due to a 404 or 410 response or equivalent, then run these substeps:
1. Mark cache group as obsolete. This cache group no longer exists for any purpose other than the processing of Document objects already associated with an application cache in the cache group.
2. Let task list be an empty list of tasks.
3. For each cache host associated with an application cache in cache group, create a task to fire a simple event named obsolete that is cancelable at the ApplicationCache singleton of the cache host, and add it to task list. The default action of these events must be, if the user agent shows caching progress, the display of some sort of user interface indicating to the user that the application is no longer available for offline use.
4. For each entry in cache group's list of pending master entries, create a task to fire a simple event that is cancelable named error (not obsolete!) at the ApplicationCache singleton of the cache host the Document for this entry, if there still is one, and add it to task list. The default action of this event must be, if the user agent shows caching progress, the display of some sort of user interface indicating to the user that the user agent failed to save the application for offline use.
5. If cache group has an application cache whose completeness flag is incomplete, then discard that application cache.
6. If appropriate, remove any user interface indicating that an update for this cache is in progress.
7. Let the status of cache group be idle.
8. For each task in task list, queue that task as a post-load task.
9. Abort the application cache download process.
Otherwise, if fetching the manifest fails in some other way (e.g. the server returns another 4xx or 5xx response or equivalent, or there is a DNS error, or the connection times out, or the user cancels the download, or the parser for manifests fails when checking the magic signature), or if the server returned a redirect, or if the resource is labeled with a MIME type other than text/cache-manifest, then run the cache failure steps.
If this is an upgrade attempt and the newly downloaded manifest is byte-for-byte identical to the manifest found in the newest application cache in cache group, or the server reported it as "304 Not Modified" or equivalent, then run these substeps:
1. Let cache be the newest application cache in cache group.
2. Let task list be an empty list of tasks.
3. For each entry in cache group's list of pending master entries, wait for the resource for this entry to have either completely downloaded or failed.
  
  If the download failed (e.g. the connection times out, or the user cancels the download), then create a task to fire a simple event that is cancelable named error at the ApplicationCache singleton of the cache host the Document for this entry, if there still is one, and add it to task list. The default action of this event must be, if the user agent shows caching progress, the display of some sort of user interface indicating to the user that the user agent failed to save the application for offline use.
  
  Otherwise, associate the Document for this entry with cache; store the resource for this entry in cache, if it isn't already there, and categorize its entry as a master entry. If the resource's URL has a <fragment> component, it must be removed from the entry in cache (application caches never include fragment identifiers).
  
  HTTP caching rules, such as Cache-Control: no-store, are ignored for the purposes of the application cache download process.
4. For each cache host associated with an application cache in cache group, create a task to fire a simple event that is cancelable named noupdate at the ApplicationCache singleton of the cache host, and add it to task list. The default action of these events must be, if the user agent shows caching progress, the display of some sort of user interface indicating to the user that the application is up to date.
5. Empty cache group's list of pending master entries.
6. If appropriate, remove any user interface indicating that an update for this cache is in progress.
7. Let the status of cache group be idle.
8. For each task in task list, queue that task as a post-load task.
9. Abort the application cache download process.
Let new cache be a newly created application cache in cache group. Set its completeness flag to incomplete.
For each entry in cache group's list of pending master entries, associate the Document for this entry with new cache.
Set the status of cache group to downloading.
For each cache host associated with an application cache in cache group, queue a post-load task to fire a simple event that is cancelable named downloading at the ApplicationCache singleton of the cache host. The default action of these events must be, if the user agent shows caching progress, the display of some sort of user interface indicating to the user that a new version is being downloaded.
Let file list be an empty list of URLs with flags.
Add all the URLs in the list of explicit entries obtained by parsing manifest to file list, each flagged with "explicit entry".
Add all the URLs in the list of fallback entries obtained by parsing manifest to file list, each flagged with "fallback entry".
If this is an upgrade attempt, then add all the URLs of master entries in the newest application cache in cache group whose completeness flag is complete to file list, each flagged with "master entry".
If any URL is in file list more than once, then merge the entries into one entry for that URL, that entry having all the flags that the original entries had.
For each URL in file list, run the following steps. These steps may be run in parallel for two or more of the URLs at a time.
1. If the resource URL being processed was flagged as neither an "explicit entry" nor or a "fallback entry", then the user agent may skip this URL.
  
  This is intended to allow user agents to expire resources not listed in the manifest from the cache. Generally, implementors are urged to use an approach that expires lesser-used resources first.
2. For each cache host associated with an application cache in cache group, queue a post-load task to fire an event with the name progress, which does not bubble, which is cancelable, and which uses the ProgressEvent interface, at the ApplicationCache singleton of the cache host. The lengthComputable attribute must be set to true, the total attribute must be set to the number of files in file list, and the loaded attribute must be set to the number of number of files in file list that have been either downloaded or skipped so far. The default action of these events must be, if the user agent shows caching progress, the display of some sort of user interface indicating to the user that a file is being downloaded in preparation for updating the application. [PROGRESS]
3. Fetch the resource, from the origin of the URL manifest URL. If this is an upgrade attempt, then use the newest application cache in cache group as an HTTP cache, and honor HTTP caching semantics (such as expiration, ETags, and so forth) with respect to that cache. User agents may also have other caches in place that are also honored.
  
  If the resource in question is already being downloaded for other reasons then the existing download process can sometimes be used for the purposes of this step, as defined by the fetching algorithm.
  
  An example of a resource that might already be being downloaded is a large image on a Web page that is being seen for the first time. The image would get downloaded to satisfy the img element on the page, as well as being listed in the cache manifest. According to the rules for fetching that image only need be downloaded once, and it can be used both for the cache and for the rendered Web page.
4. If the previous step fails (e.g. the server returns a 4xx or 5xx response or equivalent, or there is a DNS error, or the connection times out, or the user cancels the download), or if the server returned a redirect, then run the first appropriate step from the following list:
  
  If the URL being processed was flagged as an "explicit entry" or a "fallback entry"
  
  Run the cache failure steps.
  
  Redirects are fatal because they are either indicative of a network problem (e.g. a captive portal); or would allow resources to be added to the cache under URLs that differ from any URL that the networking model will allow access to, leaving orphan entries; or would allow resources to be stored under URLs different than their true URLs. All of these situations are bad.
  
  If the error was a 404 or 410 HTTP response or equivalent
  
  Skip this resource. It is dropped from the cache.
  
  Otherwise
  
  Copy the resource and its metadata from the newest application cache in cache group whose completeness flag is complete, and act as if that was the fetched resource, ignoring the resource obtained from the network.
  
  User agents may warn the user of these errors as an aid to development.
  
  These rules make errors for resources listed in the manifest fatal, while making it possible for other resources to be removed from caches when they are removed from the server, without errors, and making non-manifest resources survive server-side errors.
5. Otherwise, the fetching succeeded. Store the resource in the new cache.
6. If the URL being processed was flagged as an "explicit entry" in file list, then categorize the entry as an explicit entry.
7. If the URL being processed was flagged as a "fallback entry" in file list, then categorize the entry as a fallback entry.
8. If the URL being processed was flagged as an "master entry" in file list, then categorize the entry as a master entry.
9. As an optimization, if the resource is an HTML or XML file whose root element is an html element with a manifest attribute whose value doesn't match the manifest URL of the application cache being processed, then the user agent should mark the entry as being foreign.
For each cache host associated with an application cache in cache group, queue a post-load task to fire an event with the name progress, which does not bubble, which is cancelable, and which uses the ProgressEvent interface, at the ApplicationCache singleton of the cache host. The lengthComputable attribute must be set to true, the total and the loaded attributes must be set to the number of number of files in file list. The default action of these events must be, if the user agent shows caching progress, the display of some sort of user interface indicating to the user that all the files have been downloaded. [PROGRESS]
Store the list of fallback namespaces, and the URLs of the fallback entries that they map to, in new cache.
Store the URLs that form the new online whitelist in new cache.
Store the value of the new online whitelist wildcard flag in new cache.
For each entry in cache group's list of pending master entries, wait for the resource for this entry to have either completely downloaded or failed.

If the download failed (e.g. the connection times out, or the user cancels the download), then run these substeps:
1. Unassociate the Document for this entry from new cache.
2. Queue a post-load task to fire a simple event that is cancelable named error at the ApplicationCache singleton of the Document for this entry, if there still is one. The default action of this event must be, if the user agent shows caching progress, the display of some sort of user interface indicating to the user that the user agent failed to save the application for offline use.
3. If this is a cache attempt and this entry is the last entry in cache group's list of pending master entries, then run these further substeps:
  1. Discard cache group and its only application cache, new cache.
  2. If appropriate, remove any user interface indicating that an update for this cache is in progress.
  3. Abort the application cache download process.
4. Otherwise, remove this entry from cache group's list of pending master entries.
Otherwise, store the resource for this entry in new cache, if it isn't already there, and categorize its entry as a master entry.
Fetch the resource from manifest URL again, and let second manifest be that resource.
If the previous step failed for any reason, or if the fetching attempt involved a redirect, or if second manifest and manifest are not byte-for-byte identical, then schedule a rerun of the entire algorithm with the same parameters after a short delay, and run the cache failure steps.
Otherwise, store manifest in new cache, if it's not there already, and categorize its entry as the manifest.
Set the completeness flag of new cache to complete.
Let task list be an empty list of tasks.
If this is a cache attempt, then for each cache host associated with an application cache in cache group, create a task to fire a simple event that is cancelable named cached at the ApplicationCache singleton of the cache host, and add it to task list. The default action of these events must be, if the user agent shows caching progress, the display of some sort of user interface indicating to the user that the application has been cached and that they can now use it offline.

Otherwise, it is an upgrade attempt. For each cache host associated with an application cache in cache group, create a task to fire a simple event that is cancelable named updateready at the ApplicationCache singleton of the cache host, and add it to task list. The default action of these events must be, if the user agent shows caching progress, the display of some sort of user interface indicating to the user that a new version is available and that they can activate it by reloading the page.
If appropriate, remove any user interface indicating that an update for this cache is in progress.
Set the update status of cache group to idle.
For each task in task list, queue that task as a post-oad task.

The cache failure steps are as follows:

Let task list be an empty list of tasks.
For each entry in cache group's list of pending master entries, run the following further substeps. These steps may be run in parallel for two or more entries at a time.
1. Wait for the resource for this entry to have either completely downloaded or failed.
2. Unassociate the Document for this entry from its application cache, if it has one.
3. Create a task to fire a simple event that is cancelable named error at the ApplicationCache singleton of the Document for this entry, if there still is one, and add it to task list. The default action of these events must be, if the user agent shows caching progress, the display of some sort of user interface indicating to the user that the user agent failed to save the application for offline use.
For each cache host still associated with an application cache in cache group, create a task to fire a simple event that is cancelable named error at the ApplicationCache singleton of the cache host, and add it to task list. The default action of these events must be, if the user agent shows caching progress, the display of some sort of user interface indicating to the user that the user agent failed to save the application for offline use.
Empty cache group's list of pending master entries.
If cache group has an application cache whose completeness flag is incomplete, then discard that application cache.
If appropriate, remove any user interface indicating that an update for this cache is in progress.
Let the status of cache group be idle.
If this was a cache attempt, discard cache group altogether.
For each task in task list, queue that task as a post-load task.
Abort the application cache download process.

Attempts to fetch resources as part of the application cache download process may be done with cache-defeating semantics, to avoid problems with stale or inconsistent intermediary caches.

User agents may invoke the application cache download process, in the background, for any application cache, at any time (with no cache host). This allows user agents to keep caches primed and to update caches even before the user visits a site.

Each Document has a list of pending application cache download process tasks that is used to delay events fired by the algorithm above until the document's load event has fired. When the Document is created, the list must be empty.

When the steps above say to queue a post-load task task, where task is a task that dispatches an event on a target ApplicationCache object target, the user agent must run the appropriate steps from the following list:

If target's Document has completely loaded: Queue the task task.
Otherwise: Add task to target's Document's list of pending application cache download process tasks.

The task source for these tasks is the networking task source.

5.6.5 The application cache selection algorithm

Status: Last call for comments

When the application cache selection algorithm algorithm is invoked with a Document document and optionally a manifest URL manifest URL, the user agent must run the first applicable set of steps from the following list:

If there is a manifest URL, and document was loaded from an application cache, and the URL of the manifest of that cache's application cache group is not the same as manifest URL

Mark the entry for the resource from which document was taken in the application cache from which it was loaded as foreign.

Restart the current navigation from the top of the navigation algorithm, undoing any changes that were made as part of the initial load (changes can be avoided by ensuring that the step to update the session history with the new page is only ever completed after this application cache selection algorithm is run, though this is not required).

The navigation will not result in the same resource being loaded, because "foreign" entries are never picked during navigation.

User agents may notify the user of the inconsistency between the cache manifest and the document's own metadata, to aid in application development.

If document was loaded from an application cache

Associate document with the application cache from which it was loaded. Invoke, in the background, the application cache download process for that application cache's application cache group, with document as the cache host.

If document was loaded using HTTP GET or equivalent, and, there is a manifest URL, and manifest URL has the same origin as document

Invoke, in the background, the application cache download process for manifest URL, with document as the cache host and with the resource from which document was parsed as the master resource.

Otherwise

The Document is not associated with any application cache.

If there was a manifest URL, the user agent may report to the user that it was ignored, to aid in application development.

5.6.6 Changes to the networking model

Status: Last call for comments

When a cache host is associated with an application cache whose completeness flag is complete, any and all loads for resources related to that cache host other than those for child browsing contexts must go through the following steps instead of immediately invoking the mechanisms appropriate to that resource's scheme:

If the resource is not to be fetched using the HTTP GET mechanism or equivalent, or if its URL has a different <scheme> component than the application cache's manifest, then fetch the resource normally and abort these steps.
If the resource's URL is a master entry, the manifest, an explicit entry, or a fallback entry in the application cache, then get the resource from the cache (instead of fetching it), and abort these steps.
If there is an entry in the application cache's online whitelist that has the same origin as the resource's URL and that is a prefix match for the resource's URL, then fetch the resource normally and abort these steps.
If the resource's URL has the same origin as the manifest's URL, and there is a fallback namespace f in the application cache that is a prefix match for the resource's URL, then:

Fetch the resource normally. If this results in a redirect to a resource with another origin (indicative of a captive portal), or a 4xx or 5xx status code or equivalent, or if there were network errors (but not if the user canceled the download), then instead get, from the cache, the resource of the fallback entry corresponding to the fallback namespace f. Abort these steps.
If the application cache's online whitelist wildcard flag is open, then fetch the resource normally and abort these steps.
Fail the resource load as if there had been a generic network error.

The above algorithm ensures that so long as the online whitelist wildcard flag is blocking, resources that are not present in the manifest will always fail to load (at least, after the application cache has been primed the first time), making the testing of offline applications simpler.

5.6.7 Expiring application caches

Status: Last call for comments

As a general rule, user agents should not expire application caches, except on request from the user, or after having been left unused for an extended period of time.

Application caches and cookies have similar implications with respect to privacy (e.g. if the site can identify the user when providing the cache, it can store data in the cache that can be used for cookie resurrection). Implementors are therefore encouraged to expose application caches in a manner related to HTTP cookies, allowing caches to be expunged together with cookies and other origin-specific data.

For example, a user agent could have a "delete site-specific data" feature that clears all cookies, application caches, local storage, databases, etc, from an origin all at once.

5.6.8 Application cache API

Status: Last call for comments

interface ApplicationCache {

  // update status
  const unsigned short UNCACHED = 0;
  const unsigned short IDLE = 1;
  const unsigned short CHECKING = 2;
  const unsigned short DOWNLOADING = 3;
  const unsigned short UPDATEREADY = 4;
  const unsigned short OBSOLETE = 5;
  readonly attribute unsigned short status;

  // updates
  void update();
  void swapCache();

  // events
           attribute Function onchecking;
           attribute Function onerror;
           attribute Function onnoupdate;
           attribute Function ondownloading;
           attribute Function onprogress;
           attribute Function onupdateready;
           attribute Function oncached;
           attribute Function onobsolete;
};
ApplicationCache implements EventTarget;

cache = window . applicationCache

(In a window.) Returns the ApplicationCache object that applies to the active document of that Window.

cache = self . applicationCache

(In a shared worker.) Returns the ApplicationCache object that applies to the current shared worker. [WEBWORKERS]

cache . status

Returns the current status of the application cache, as given by the constants defined below.

cache . update()

Invokes the application cache download process.

Throws an INVALID_STATE_ERR exception if there is no application cache to update.

cache . swapCache()

Switches to the most recent application cache, if there is a newer one. If there isn't, throws an INVALID_STATE_ERR exception.

This does not cause previously-loaded resources to be reloaded; for example, images do not suddenly get reloaded and style sheets and scripts do not get reparsed or reevaluated. The only change is that subsequent requests for cached resources will obtain the newer copies.

There is a one-to-one mapping from cache hosts to ApplicationCache objects. The applicationCache attribute on Window objects must return the ApplicationCache object associated with the Window object's active document. The applicationCache attribute on SharedWorkerGlobalScope objects must return the ApplicationCache object associated with the worker. [WEBWORKERS]

A Window or SharedWorkerGlobalScope object has an associated ApplicationCache object even if that cache host has no actual application cache.

The status attribute, on getting, must return the current state of the application cache that the ApplicationCache object's cache host is associated with, if any. This must be the appropriate value from the following list:

UNCACHED (numeric value 0): The ApplicationCache object's cache host is not associated with an application cache at this time.
IDLE (numeric value 1): The ApplicationCache object's cache host is associated with an application cache whose application cache group's update status is idle, and that application cache is the newest cache in its application cache group, and the application cache group is not marked as obsolete.
CHECKING (numeric value 2): The ApplicationCache object's cache host is associated with an application cache whose application cache group's update status is checking.
DOWNLOADING (numeric value 3): The ApplicationCache object's cache host is associated with an application cache whose application cache group's update status is downloading.
UPDATEREADY (numeric value 4): The ApplicationCache object's cache host is associated with an application cache whose application cache group's update status is idle, and whose application cache group is not marked as obsolete, but that application cache is not the newest cache in its group.
OBSOLETE (numeric value 5): The ApplicationCache object's cache host is associated with an application cache whose application cache group is marked as obsolete.

If the update() method is invoked, the user agent must invoke the application cache download process, in the background, for the application cache with which the ApplicationCache object's cache host is associated, but without giving that cache host to the algorithm. If there is no such application cache, or if it is marked as obsolete, then the method must raise an INVALID_STATE_ERR exception instead.

If the swapCache() method is invoked, the user agent must run the following steps:

Check that ApplicationCache object's cache host is associated with an application cache. If it is not, then raise an INVALID_STATE_ERR exception and abort these steps.
Let cache be the application cache with which the ApplicationCache object's cache host is associated. (By definition, this is the same as the one that was found in the previous step.)
If cache's application cache group is marked as obsolete, then unassociate the ApplicationCache object's cache host from cache and abort these steps. (Resources will now load from the network instead of the cache.)
Check that there is an application cache in the same application cache group as cache whose completeness flag is complete and that is newer than cache. If there is not, then raise an INVALID_STATE_ERR exception and abort these steps.
Let new cache be the newest application cache in the same application cache group as cache whose completeness flag is complete.
Unassociate the ApplicationCache object's cache host from cache and instead associate it with new cache.

The following are the event handlers (and their corresponding event handler event types) that must be supported, as IDL attributes, by all objects implementing the ApplicationCache interface:

Event handler	Event handler event type
`onchecking`	`checking`
`onerror`	`error`
`onnoupdate`	`noupdate`
`ondownloading`	`downloading`
`onprogress`	`progress`
`onupdateready`	`updateready`
`oncached`	`cached`
`onobsolete`	`obsolete`

5.6.9 Browser state

Status: Last call for comments

window . navigator . onLine: Returns false if the user agent is definitely offline (disconnected from the network). Returns true if the user agent might be online.

The navigator.onLine attribute must return false if the user agent will not contact the network when the user follows links or when a script requests a remote page (or knows that such an attempt would fail), and must return true otherwise.

When the value that would be returned by the navigator.onLine attribute of the Window changes from true to false, the user agent must queue a task to fire a simple event named offline at the Window object.

On the other hand, when the value that would be returned by the navigator.onLine attribute of the Window changes from false to true, the user agent must queue a task to fire a simple event named online at the Window object.

The task source for these tasks is the networking task source.

This attribute is inherently unreliable. A computer can be connected to a network without having Internet access.

6 Web application APIs

6.1 Scripting

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6.1.1 Introduction

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Various mechanisms can cause author-provided executable code to run in the context of a document. These mechanisms include, but are probably not limited to:

Processing of script elements.
Processing of inline javascript: URLs (e.g. the src attribute of img elements, or an @import rule in a CSS style element block).
Event handlers, whether registered through the DOM using addEventListener(), by explicit event handler content attributes, by event handler IDL attributes, or otherwise.
Processing of technologies like XBL or SVG that have their own scripting features.

6.1.2 Enabling and disabling scripting

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Scripting is enabled in a browsing context when all of the following conditions are true:

The user agent supports scripting.
The user has not disabled scripting for this browsing context at this time. (User agents may provide users with the option to disable scripting globally, or in a finer-grained manner, e.g. on a per-origin basis.)
The browsing context did not have the sandboxed scripts browsing context flag set when the browsing context's active document was created.

Scripting is disabled in a browsing context when any of the above conditions are false (i.e. when scripting is not enabled).

Scripting is enabled for a node if the Document object of the node (the node itself, if it is itself a Document object) has an associated browsing context, and scripting is enabled in that browsing context.

Scripting is disabled for a node if there is no such browsing context, or if scripting is disabled in that browsing context.

6.1.3 Processing model

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6.1.3.1 Definitions

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A script has:

A script execution environment

The characteristics of the script execution environment depend on the language, and are not defined by this specification.

In JavaScript, the script execution environment consists of the interpreter, the stack of execution contexts, the global code and function code and the Function objects resulting, and so forth.

A list of code entry-points

Each code entry-point represents a block of executable code that the script exposes to other scripts and to the user agent.

Each Function object in a JavaScript script execution environment has a corresponding code entry-point, for instance.

The main program code of the script, if any, is the initial code entry-point. Typically, the code corresponding to this entry-point is executed immediately after the script is parsed.

In JavaScript, this corresponds to the execution context of the global code.

A relationship with the script's global object

An object that provides the APIs that the code can use.

This is typically a Window object. In JavaScript, this corresponds to the global object.

When a script's global object is an empty object, it can't do anything that interacts with the environment.

If the script's global object is a Window object, then in JavaScript, the ThisBinding of the global execution context for this script must be the Window object's WindowProxy object, rather than the global object. [ECMA262]

This is a willful violation of the JavaScript specification current at the time of writing (ECMAScript edition 5, as defined in section 10.4.1.1 Initial Global Execution Context, step 3). The JavaScript specification requires that the this keyword in the global scope return the global object, but this is not compatible with the security design prevalent in implementations as specified herein. [ECMA262]

A relationship with the script's browsing context

A browsing context that is assigned responsibility for actions taken by the script.

When a script creates and navigates a new top-level browsing context, the opener attribute of the new browsing context's Window object will be set to the script's browsing context's WindowProxy object.

A relationship with the script's document

A Document that is assigned responsibility for actions taken by the script.

When a script fetches a resource, the current address of the script's document will be used to set the Referer (sic) header.

A URL character encoding

A character encoding, set when the script is created, used to encode URLs. If the character encoding is set from another source, e.g. a document's character encoding, then the script's URL character encoding must follow the source, so that if the source's changes, so does the script's.

A base URL

A URL, set when the script is created, used to resolve relative URLs. If the base URL is set from another source, e.g. a document base URL, then the script's base URL must follow the source, so that if the source's changes, so does the script's.

6.1.3.2 Calling scripts

Status: Last call for comments

When a user agent is to jump to a code entry-point for a script, for example to invoke an event listener defined in that script, the user agent must run the following steps:

If the script's global object is a Window object whose Document object is not fully active, then abort these steps without doing anything. The callback is not fired.
Set the entry script to be the script being invoked.
Make the script execution environment for the script execute the code for the given code entry-point.
Set the entry script back to whatever it was when this algorithm started.

This algorithm is not invoked by one script calling another.

6.1.3.3 Creating scripts

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When the specification says that a script is to be created, given some script source, its scripting language, a global object, a browsing context, a URL character encoding, and a base URL, the user agent must run the following steps:

If scripting is disabled for browsing context passed to this algorithm, then abort these steps, as if the script did nothing but return void.
Set up a script execution environment as appropriate for the scripting language.
Parse/compile/initialize the source of the script using the script execution environment, as appropriate for the scripting language, and thus obtain the list of code entry-points for the script. If the semantics of the scripting language and the given source code are such that there is executable code to be immediately run, then the initial code entry-point is the entry-point for that code.
Set up the script's global object, the script's browsing context, the script's document, the script's URL character encoding, and the script's base URL from the settings passed to this algorithm.
Jump to the script's initial code entry-point.

When the user agent is to create an impotent script, given some script source, its scripting language, and a browsing context, the user agent must create a script, using the given script source and scripting language, using a new empty object as the global object, and using the given browsing context as the browsing context. The URL character encoding and base URL for the resulting script are not important as no APIs are exposed to the script.

When the specification says that a script is to be created from a node node, given some script source and its scripting language, the user agent must create a script, using the given script source and scripting language, and using the script settings determined from the node node.

The script settings determined from the node node are computed as follows:

Let document be the Document of node (or node itself if it is a Document).
The browsing context is the browsing context of document.
The global object is the Window object of document.
The URL character encoding is the character encoding of document. (This is a reference, not a copy.)
The base URL is the base URL of document. (This is a reference, not a copy.)

6.1.3.4 Killing scripts

Status: Last call for comments

User agents may impose resource limitations on scripts, for example CPU quotas, memory limits, total execution time limits, or bandwidth limitations. When a script exceeds a limit, the user agent may either throw a QUOTA_EXCEEDED_ERR exception, abort the script without an exception, prompt the user, or throttle script execution.

For example, the following script never terminates. A user agent could, after waiting for a few seconds, prompt the user to either terminate the script or let it continue.

<script>
 while (true) { /* loop */ }
</script>

User agents are encouraged to allow users to disable scripting whenever the user is prompted either by a script (e.g. using the window.alert() API) or because of a script's actions (e.g. because it has exceeded a time limit).

If scripting is disabled while a script is executing, the script should be terminated immediately.

6.1.4 Event loops

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6.1.4.1 Definitions

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To coordinate events, user interaction, scripts, rendering, networking, and so forth, user agents must use event loops as described in this section.

There must be at least one event loop per user agent, and at most one event loop per unit of related similar-origin browsing contexts.

An event loop always has at least one browsing context. If an event loop's browsing contexts all go away, then the event loop goes away as well. A browsing context always has an event loop coordinating its activities.

Other specifications can define new kinds of event loops that aren't associated with browsing contexts; in particular, the Web Workers specification does so.

An event loop has one or more task queues. A task queue is an ordered list of tasks, which can be:

Events

Asynchronously dispatching an Event object at a particular EventTarget object is a task.

Not all events are dispatched using the task queue, many are dispatched synchronously during other tasks.

Parsing

The HTML parser tokenizing a single byte, and then processing any resulting tokens, is a task.

Callbacks

Calling a callback asynchronously is a task.

Using a resource

When an algorithm fetches a resource, if the fetching occurs asynchronously then the processing of the resource once some or all of the resource is available is a task.

Reacting to DOM manipulation

Some elements have tasks that trigger in response to DOM manipulation, e.g. when that element is inserted into the document.

When a user agent is to queue a task, it must add the given task to one of the task queues of the relevant event loop. All the tasks from one particular task source (e.g. the callbacks generated by timers, the events dispatched for mouse movements, the tasks queued for the parser) must always be added to the same task queue, but tasks from different task sources may be placed in different task queues.

For example, a user agent could have one task queue for mouse and key events (the user interaction task source), and another for everything else. The user agent could then give keyboard and mouse events preference over other tasks three quarters of the time, keeping the interface responsive but not starving other task queues, and never processing events from any one task source out of order.

Each task that is queued onto a task queue of an event loop defined by this specification is associated with a Document; if the task was queued in the context of an element, then it is the element's Document; if the task was queued in the context of a browsing context, then it is the browsing context's active document at the time the task was queued; if the task was queued by or for a script then the document is the script's document.

A user agent is required to have one storage mutex. This mutex is used to control access to shared state like cookies. At any one point, the storage mutex is either free, or owned by a particular event loop or instance of the fetching algorithm.

Whenever a script calls into a plugin, and whenever a plugin calls into a script, the user agent must release the storage mutex.

6.1.4.2 Processing model

Status: Last call for comments

An event loop must continually run through the following steps for as long as it exists:

Run the oldest task on one of the event loop's task queues, ignoring tasks whose associated Documents are not fully active. The user agent may pick any task queue.
If the storage mutex is now owned by the event loop, release it so that it is once again free.
Remove that task from its task queue.
If any asynchronously-running algorithms are awaiting a stable state, then run their synchronous section and then resume running their asynchronous algorithm.

A synchronous section never mutates the DOM, runs any script, or has any other side-effects.

Steps in synchronous sections are marked with ⌛.
If necessary, update the rendering or user interface of any Document or browsing context to reflect the current state.
Return to the first step of the event loop.

When an algorithm says to spin the event loop until a condition goal is met, the user agent must run the following steps:

Let task source be the task source of the currently running task.
Stop the currently running task, allowing the event loop to resume, but continue these steps asynchronously.
Wait until the condition goal is met.
Queue a task to continue running these steps, using the task source task source. Wait until this task runs before continuing these steps.
Return to the caller.

Some of the algorithms in this specification, for historical reasons, require the user agent to pause while running a task until some condition has been met. While a user agent has a paused task, the corresponding event loop must not run further tasks, and any script in the currently running task must block. User agents should remain responsive to user input while paused, however, albeit in a reduced capacity since the event loop will not be doing anything.

When a user agent is to obtain the storage mutex as part of running a task, it must run through the following steps:

If the storage mutex is already owned by this task's event loop, then abort these steps.
Otherwise, pause until the storage mutex can be taken by the event loop.
Take ownership of the storage mutex.

6.1.4.3 Generic task sources

Status: Last call for comments

The following task sources are used by a number of mostly unrelated features in this and other specifications.

The DOM manipulation task source

This task source is used for features that react to DOM manipulations, such as things that happen asynchronously when an element is inserted into the document.

The user interaction task source

This task source is used for features that react to user interaction, for example keyboard or mouse input.

Asynchronous events sent in response to user input (e.g. click events) must be dispatched using tasks queued with the user interaction task source. [DOMEVENTS]

The networking task source

This task source is used for features that trigger in response to network activity.

The history traversal task source

This task source is used to queue calls to history.back() and similar APIs.

6.1.5 The `javascript:` protocol

Status: Last call for comments

When a URL using the javascript: protocol is dereferenced, the user agent must run the following steps:

Let the script source be the string obtained using the content retrieval operation defined for javascript: URLs. [JSURL]
Use the appropriate step from the following list:

If a browsing context is being navigated to a javascript: URL, and the active document of that browsing context has the same origin as the script given by that URL

Let address be the address of the active document of the browsing context being navigated.

If address is about:blank, and the browsing context being navigated has a creator browsing context, then let address be the address of the creator Document instead.

Create a script from the Document node of the active document, using the aforementioned script source, and assuming the scripting language is JavaScript.

Let result be the return value of the initial code entry-point of this script. If an exception was raised, let result be void instead. (The result will be void also if scripting is disabled.)

When it comes time to set the document's address in the navigation algorithm, use address as the override URL.

If the Document object of the element, attribute, or style sheet from which the javascript: URL was reached has an associated browsing context

Create an impotent script using the aforementioned script source, with the scripting language set to JavaScript, and with the Document's object's browsing context as the browsing context.

Let result be the return value of the initial code entry-point of this script. If an exception was raised, let result be void instead. (The result will be void also if scripting is disabled.)

Otherwise

Let result be void.
If the result of executing the script is void (there is no return value), then the URL must be treated in a manner equivalent to an HTTP resource with an HTTP 204 No Content response.

Otherwise, the URL must be treated in a manner equivalent to an HTTP resource with a 200 OK response whose Content-Type metadata is text/html and whose response body is the return value converted to a string value.

Certain contexts, in particular img elements, ignore the Content-Type metadata.

So for example a javascript: URL for a src attribute of an img element would be evaluated in the context of an empty object as soon as the attribute is set; it would then be sniffed to determine the image type and decoded as an image.

A javascript: URL in an href attribute of an a element would only be evaluated when the link was followed.

The src attribute of an iframe element would be evaluated in the context of the iframe's own browsing context; once evaluated, its return value (if it was not void) would replace that browsing context's document, thus changing the variables visible in that browsing context.

6.1.6 Events

Status: Last call for comments

6.1.6.1 Event handlers

Status: Last call for comments

Many objects can have event handlers specified. These act as bubbling event listeners for the object on which they are specified.

An event handler can either have the value null or be set to a Function object. Initially, event handlers must be set to null.

Event handlers are exposed in one or two ways.

The first way, common to all event handlers, is as an event handler IDL attribute.

The second way is as an event handler content attribute. Event handlers on HTML elements and some of the event handlers on Window objects are exposed in this way.

Event handler IDL attributes, on setting, must set the corresponding event handler to their new value, and on getting, must return whatever the current value of the corresponding event handler is (possibly null).

If an event handler IDL attribute exposes an event handler of an object that doesn't exist, it must always return null on getting and must do nothing on setting.

This can happen in particular for event handler IDL attribute on body elements that do not have corresponding Window objects.

Certain event handler IDL attributes have additional requirements, in particular the onmessage attribute of MessagePort objects.

Event handler content attributes, when specified, must contain valid JavaScript code matching the FunctionBody production. [ECMA262]

When an event handler content attribute is set, if the element is owned by a Document that is in a browsing context, and scripting is enabled for that browsing context, the user agent must run the following steps to create a script after setting the content attribute to its new value:

Set up a script execution environment for JavaScript.
Using this script execution environment, create a function object (as defined in ECMAScript edition 5 section 13.2 Creating Function Objects), with:
Parameter list FormalParameterList

If the attribute is the onerror attribute of the Window object

Let the function have three arguments, named event, source, and fileno.

Otherwise

Let the function have a single argument called event.

Function body FunctionBody

The event handler content attribute's new value.

Lexical Environment Scope
1. Let Scope be the result of NewObjectEnvironment(the element's Document, the global environment).
2. If the element has a form owner, let Scope be the result of NewObjectEnvironment(the element's form owner, Scope).
3. Let Scope be the result of NewObjectEnvironment(the element's object, Scope).
NewObjectEnvironment() is defined in ECMAScript edition 5 section 10.2.2.3 NewObjectEnvironment (O, E). [ECMA262]
Boolean flag Strict

False.
Let this new function be the only entry in the script's list of code entry-points.
If the previous steps failed to compile the script, then set the corresponding event handler to null and abort these steps.
Set up the script's global object, the script's browsing context, the script's document, the script's URL character encoding, and the script's base URL from the script settings determined from the node on which the attribute is being set.
Set the corresponding event handler to the aforementioned function.

When an event handler content attribute is removed, the user agent must set the corresponding event handler to null.

When an event handler content attribute is set on an element owned by a Document that is not in a browsing context, the corresponding event handler is not changed.

All event handlers on an object, whether an element or some other object, and whether set to null or to a Function object, must be registered as event listeners on the object when it is created, as if the addEventListener() method on the object's EventTarget interface had been invoked, with the event type (type argument) equal to the type corresponding to the event handler (the event handler event type), the listener set to be a target and bubbling phase listener (useCapture argument set to false), and the event listener itself (listener argument) set to do nothing while the event handler's value is not a Function object, and set to invoke the call() callback of the Function object associated with the event handler otherwise.

Event handlers therefore always fire before event listeners attached using addEventListener().

The listener argument is emphatically not the event handler itself.

The interfaces implemented by the event object do not influence whether an event handler is triggered or not.

When an event handler's Function object is invoked, its call() callback must be invoked with one argument, set to the Event object of the event in question.

The handler's return value must then be processed as follows:

If the event type is mouseover: If the return value is a boolean with the value true, then the event must be canceled.
If the event object is a BeforeUnloadEvent object: If the return value is a string, and the event object's returnValue attribute's value is the empty string, then set the returnValue attribute's value to the return value.
Otherwise: If the return value is a boolean with the value false, then the event must be canceled.

The Function interface represents a function in the scripting language being used. It is represented in IDL as follows:

[Callback=FunctionOnly, NoInterfaceObject]
interface Function {
  any call(in any... arguments);
};

The call(...) method is the object's callback.

In JavaScript, any Function object implements this interface.

If the Function object is a JavaScript Function, then when it is invoked by the user agent, the user agent must set the thisArg (as defined by ECMAScript edition 5 section 10.4.3 Entering Function Code) to the event handler's object. [ECMA262]

For example, the following document fragment:

<body onload="alert(this)" onclick="alert(this)">

...leads to an alert saying "[object Window]" when the document is loaded, and an alert saying "[object HTMLBodyElement]" whenever the user clicks something in the page.

The return value of the function is affects whether the event is canceled or not: as described above, if the return value is false, the event is canceled (except for mouseover events, where the return value has to be true to cancel the event). With beforeunload events, the value is instead used to determine the message to show the user.

6.1.6.2 Event handlers on elements, `Document` objects, and `Window` objects

The following are the event handlers (and their corresponding event handler event types) that must be supported by all HTML elements, as both content attributes and IDL attributes, and on Document and Window objects, as IDL attributes.

Event handler	Event handler event type
`onabort`	`abort`
`oncanplay`	`canplay`
`oncanplaythrough`	`canplaythrough`
`onchange`	`change`
`onclick`	`click`
`oncontextmenu`	`contextmenu`
`ondblclick`	`dblclick`
`ondrag`	`drag`
`ondragend`	`dragend`
`ondragenter`	`dragenter`
`ondragleave`	`dragleave`
`ondragover`	`dragover`
`ondragstart`	`dragstart`
`ondrop`	`drop`
`ondurationchange`	`durationchange`
`onemptied`	`emptied`
`onended`	`ended`
`onformchange`	`formchange`
`onforminput`	`forminput`
`oninput`	`input`
`oninvalid`	`invalid`
`onkeydown`	`keydown`
`onkeypress`	`keypress`
`onkeyup`	`keyup`
`onloadeddata`	`loadeddata`
`onloadedmetadata`	`loadedmetadata`
`onloadstart`	`loadstart`
`onmousedown`	`mousedown`
`onmousemove`	`mousemove`
`onmouseout`	`mouseout`
`onmouseover`	`mouseover`
`onmouseup`	`mouseup`
`onmousewheel`	`mousewheel`
`onpause`	`pause`
`onplay`	`play`
`onplaying`	`playing`
`onprogress`	`progress`
`onratechange`	`ratechange`
`onreadystatechange`	`readystatechange`
`onscroll`	`scroll`
`onseeked`	`seeked`
`onseeking`	`seeking`
`onselect`	`select`
`onshow`	`show`
`onstalled`	`stalled`
`onsubmit`	`submit`
`onsuspend`	`suspend`
`ontimeupdate`	`timeupdate`
`onvolumechange`	`volumechange`
`onwaiting`	`waiting`

The following are the event handlers (and their corresponding event handler event types) that must be supported by all HTML elements other than body, as both content attributes and IDL attributes, and on Document objects, as IDL attributes:

Event handler	Event handler event type
`onblur`	`blur`
`onerror`	`error`
`onfocus`	`focus`
`onload`	`load`

The following are the event handlers (and their corresponding event handler event types) that must be supported by Window objects, as IDL attributes on the Window object, and with corresponding content attributes and IDL attributes exposed on the body and frameset elements:

Event handler	Event handler event type
`onafterprint`	`afterprint`
`onbeforeprint`	`beforeprint`
`onbeforeunload`	`beforeunload`
`onblur`	`blur`
`onerror`	`error`
`onfocus`	`focus`
`onhashchange`	`hashchange`
`onload`	`load`
`onmessage`	`message`
`onoffline`	`offline`
`ononline`	`online`
`onpagehide`	`pagehide`
`onpageshow`	`pageshow`
`onpopstate`	`popstate`
`onredo`	`redo`
`onresize`	`resize`
`onstorage`	`storage`
`onundo`	`undo`
`onunload`	`unload`

The onerror handler is also used for reporting script errors.

6.1.6.3 Event firing

Status: Last call for comments

Certain operations and methods are defined as firing events on elements. For example, the click() method on the HTMLElement interface is defined as firing a click event on the element. [DOMEVENTS]

Firing a click event means that a click event, which bubbles and is cancelable, and which uses the MouseEvent interface, must be dispatched at the given target. The event object must have its screenX, screenY, clientX, clientY, and button attributes set to 0, its ctrlKey, shiftKey, altKey, and metaKey attributes set according to the current state of the key input device, if any (false for any keys that are not available), its detail attribute set to 1, and its relatedTarget attribute set to null. The getModifierState() method on the object must return values appropriately describing the state of the key input device at the time the event is created.

Firing a simple event named e means that an event with the name e, which does not bubble (except where otherwise stated) and is not cancelable (except where otherwise stated), and which uses the Event interface, must be dispatched at the given target.

The default action of these event is to do nothing except where otherwise stated.

6.1.6.4 Events and the `Window` object

Status: Last call for comments

When an event is dispatched at a DOM node in a Document in a browsing context, if the event is not a load event, the user agent must also dispatch the event to the Window, as follows:

In the capture phase, the event must propagate to the Window object before propagating to any of the nodes, as if the Window object was the parent of the Document in the dispatch chain.
In the bubble phase, the event must propagate up to the Window object at the end of the phase, unless bubbling has been prevented, again as if the Window object was the parent of the Document in the dispatch chain.

6.1.6.5 Runtime script errors

Status: Last call for comments

This section only applies to user agents that support scripting in general and JavaScript in particular.

Whenever an uncaught runtime script error occurs in one of the scripts associated with a Document, the user agent must report the error using the onerror event handler of the script's global object. If the error is still not handled after this, then the error may be reported to the user.

When the user agent is required to report an error error using the event handler onerror, it must run these steps, after which the error is either handled or not handled:

If the value of onerror is a Function

The function must be invoked with three arguments. The three arguments passed to the function are all DOMStrings; the first must give the message that the UA is considering reporting, the second must give the absolute URL of the resource in which the error occurred, and the third must give the line number in that resource on which the error occurred.

If the function returns false, then the error is handled. Otherwise, the error is not handled.

Any uncaught exceptions thrown or errors caused by this function may be reported to the user immediately after the error that the function was called for; the report an error algorithm must not be used to handle exceptions thrown or errors caused by this function.

Otherwise

The error is not handled.

6.2 Timers

Status: Last call for comments

The setTimeout() and setInterval() methods allow authors to schedule timer-based callbacks.

[Supplemental, NoInterfaceObject]
interface WindowTimers {
  long setTimeout(in any handler, in optional any timeout, in any... args);
  void clearTimeout(in long handle);
  long setInterval(in any handler, in optional any timeout, in any... args);
  void clearInterval(in long handle);
};
Window implements WindowTimers;

handle = window . setTimeout( handler [, timeout [, arguments ] ] ): Schedules a timeout to run handler after timeout milliseconds. Any arguments are passed straight through to the handler.
handle = window . setTimeout( code [, timeout ] ): Schedules a timeout to compile and run code after timeout milliseconds.
window . clearTimeout( handle ): Cancels the timeout set with setTimeout() identified by handle.
handle = window . setInterval( handler [, timeout [, arguments ] ] ): Schedules a timeout to run handler every timeout milliseconds. Any arguments are passed straight through to the handler.
handle = window . setInterval( code [, timeout ] ): Schedules a timeout to compile and run code every timeout milliseconds.
window . clearInterval( handle ): Cancels the timeout set with setInterval() identified by handle.

This API does not guarantee that timers will fire exactly on schedule. Delays due to CPU load, other tasks, etc, are to be expected.

The WindowTimers interface adds to the Window interface and the WorkerUtils interface (part of Web Workers).

Each object that implements the WindowTimers interface has a list of active timeouts and a list of active intervals. Each entry in these lists is identified by a number, which must be unique within its list for the lifetime of the object that implements the WindowTimers interface.

The setTimeout() method must run the following steps:

Let handle be a user-agent-defined integer that is greater than zero that will identify the timeout to be set by this call.
Add an entry to the list of active timeouts for handle.
Get the timed task handle in the list of active timeouts, and let task be the result.
Get the timeout, and let timeout be the result.
If the currently running task is a task that was created by the setTimeout() method, and timeout is less than 4, then increase timeout to 4.
Return handle, and then continue running this algorithm asynchronously.
If the method context is a Window object, wait until the Document associated with the method context has been fully active for a further timeout milliseconds (not necessarily consecutively).

Otherwise, if the method context is a WorkerUtils object, wait until timeout milliseconds have passed with the worker not suspended (not necessarily consecutively).

Otherwise, act as described in the specification that defines that the WindowTimers interface is implemented by some other object.
Wait until any invocations of this algorithm started before this one whose timeout is equal to or less than this one's have completed.
Queue the task task.

The clearTimeout() method must clear the entry identified as handle from the list of active timeouts of the WindowTimers object on which the method was invoked, where handle is the argument passed to the method.

The setInterval() method must run the following steps:

Let handle be a user-agent-defined integer that is greater than zero that will identify the interval to be set by this call.
Add an entry to the list of active intervals for handle.
Get the timed task handle in the list of active intervals, and let task be the result.
Get the timeout, and let timeout be the result.
If timeout is less than 10, then increase timeout to 10.
Return handle, and then continue running this algorithm asynchronously.
Wait: If the method context is a Window object, wait until the Document associated with the method context has been fully active for a further interval milliseconds (not necessarily consecutively).

Otherwise, if the method context is a WorkerUtils object, wait until interval milliseconds have passed with the worker not suspended (not necessarily consecutively).

Otherwise, act as described in the specification that defines that the WindowTimers interface is implemented by some other object.
Queue the task task.
Return to the step labeled wait.

The clearInterval() method must clear the entry identified as handle from the list of active intervals of the WindowTimers object on which the method was invoked, where handle is the argument passed to the method.

The method context, when referenced by the algorithms in this section, is the object on which the method for which the algorithm is running is implemented (a Window or WorkerUtils object).

When the above methods are invoked and try to get the timed task handle in list list, they must run the following steps:

If the first argument to the invoked method is an object that has an internal [[Call]] method, then return a task that checks if the entry for handle in list has been cleared, and if it has not, calls the aforementioned [[Call]] method with as its arguments the third and subsequent arguments to the invoked method (if any), and abort these steps.

Otherwise, continue with the remaining steps.
Apply the ToString() abstract operation to the first argument to the method, and let script source be the result. [ECMA262]
Let script language be JavaScript.
If the method context is a Window object, let global object be the method context, let browsing context be the browsing context with which global object is associated, let character encoding be the character encoding of the Document associated with global object (this is a reference, not a copy), and let base URL be the base URL of the Document associated with global object (this is a reference, not a copy).

Otherwise, if the method context is a WorkerUtils object, let global object, browsing context, document, character encoding, and base URL be the script's global object, script's browsing context, script's document, script's URL character encoding, and script's base URL (respectively) of the script that the run a worker algorithm created when it created the method context.

Otherwise, act as described in the specification that defines that the WindowTimers interface is implemented by some other object.
Return a task that checks if the entry for handle in list has been cleared, and if it has not, creates a script using script source as the script source, scripting language as the scripting language, global object as the global object, browsing context as the browsing context, document as the document, character encoding as the URL character encoding, and base URL as the base URL.

When the above methods are to get the timeout, they must run the following steps:

Let timeout be the second argument to the method, or zero if the argument was omitted.
Apply the ToString() abstract operation to timeout, and let timeout be the result. [ECMA262]
Apply the ToNumber() abstract operation to timeout, and let timeout be the result. [ECMA262]
If timeout is an Infinity value, a Not-a-Number (NaN) value, or negative, let timeout be zero.
Round timeout down to the nearest integer, and let timeout be the result.
Return timeout.

The task source for these tasks is the timer task source.

6.3 User prompts

Status: Last call for comments

6.3.1 Simple dialogs

Status: Last call for comments

window . alert(message)

Displays a modal alert with the given message, and waits for the user to dismiss it.

A call to the navigator.yieldForStorageUpdates() method is implied when this method is invoked.

result = window . confirm(message)

Displays a modal OK/Cancel prompt with the given message, waits for the user to dismiss it, and returns true if the user clicks OK and false if the user clicks Cancel.

A call to the navigator.yieldForStorageUpdates() method is implied when this method is invoked.

result = window . prompt(message [, default] )

Displays a modal text field prompt with the given message, waits for the user to dismiss it, and returns the value that the user entered. If the user cancels the prompt, then returns null instead. If the second argument is present, then the given value is used as a default.

A call to the navigator.yieldForStorageUpdates() method is implied when this method is invoked.

The alert(message) method, when invoked, must release the storage mutex and show the given message to the user. The user agent may make the method wait for the user to acknowledge the message before returning; if so, the user agent must pause while the method is waiting.

The confirm(message) method, when invoked, must release the storage mutex and show the given message to the user, and ask the user to respond with a positive or negative response. The user agent must then pause as the method waits for the user's response. If the user responds positively, the method must return true, and if the user responds negatively, the method must return false.

The prompt(message, default) method, when invoked, must release the storage mutex, show the given message to the user, and ask the user to either respond with a string value or abort. The user agent must then pause as the method waits for the user's response. The second argument is optional. If the second argument (default) is present, then the response must be defaulted to the value given by default. If the user aborts, then the method must return null; otherwise, the method must return the string that the user responded with.

6.3.2 Printing

Status: Last call for comments

window . print()

Prompts the user to print the page.

A call to the navigator.yieldForStorageUpdates() method is implied when this method is invoked.

The print() method, when invoked, must run the printing steps.

User agents should also run the printing steps whenever the user asks for the opportunity to obtain a physical form (e.g. printed copy), or the representation of a physical form (e.g. PDF copy), of a document.

The printing steps are as follows:

The user agent may display a message to the user and/or may abort these steps.

For instance, a kiosk browser could silently ignore any invocations of the print() method.

For instance, a browser on a mobile device could detect that there are no printers in the vicinity and display a message saying so before continuing to offer a "save to PDF" option.
The user agent must fire a simple event named beforeprint at the Window object of the Document that is being printed, as well as any nested browsing contexts in it.

The beforeprint event can be used to annotate the printed copy, for instance adding the time at which the document was printed.
The user agent must release the storage mutex.
The user agent should offer the user the opportunity to obtain a physical form (or the representation of a physical form) of the document. The user agent may wait for the user to either accept or decline before returning; if so, the user agent must pause while the method is waiting. Even if the user agent doesn't wait at this point, the user agent must use the state of the relevant documents as they are at this point in the algorithm if and when it eventually creates the alternate form.
The user agent must fire a simple event named afterprint at the Window object of the Document that is being printed, as well as any nested browsing contexts in it.

The afterprint event can be used to revert annotations added in the earlier event, as well as showing post-printing UI. For instance, if a page is walking the user through the steps of applying for a home loan, the script could automatically advance to the next step after having printed a form or other.

6.3.3 Dialogs implemented using separate documents

Status: Last call for comments

result = window . showModalDialog(url [, argument] )

Prompts the user with the given page, waits for that page to close, and returns the return value.

A call to the navigator.yieldForStorageUpdates() method is implied when this method is invoked.

The showModalDialog(url, argument) method, when invoked, must cause the user agent to run the following steps:

Resolve url relative to the entry script's base URL.

If this fails, then throw a SYNTAX_ERR exception and abort these steps.
Release the storage mutex.
If the user agent is configured such that this invocation of showModalDialog() is somehow disabled, then return the empty string and abort these steps.

User agents are expected to disable this method in certain cases to avoid user annoyance (e.g. as part of their popup blocker feature). For instance, a user agent could require that a site be white-listed before enabling this method, or the user agent could be configured to only allow one modal dialog at a time.
Let the list of background browsing contexts be a list of all the browsing contexts that:
- are part of the same unit of related browsing contexts as the browsing context of the Window object on which the showModalDialog() method was called, and that
- have an active document whose origin is the same as the origin of the script that called the showModalDialog() method at the time the method was called,
...as well as any browsing contexts that are nested inside any of the browsing contexts matching those conditions.
Disable the user interface for all the browsing contexts in the list of background browsing contexts. This should prevent the user from navigating those browsing contexts, causing events to be sent to those browsing context, or editing any content in those browsing contexts. However, it does not prevent those browsing contexts from receiving events from sources other than the user, from running scripts, from running animations, and so forth.
Create a new auxiliary browsing context, with the opener browsing context being the browsing context of the Window object on which the showModalDialog() method was called. The new auxiliary browsing context has no name.

This browsing context's Documents' Window objects all implement the WindowModal interface.
Let the dialog arguments of the new browsing context be set to the value of argument, or the 'undefined' value if the argument was omitted.
Let the dialog arguments' origin be the origin of the script that called the showModalDialog() method.
Navigate the new browsing context to the absolute URL that resulted from resolving url earlier, with replacement enabled, and with the browsing context of the script that invoked the method as the source browsing context.
Spin the event loop until the new browsing context is closed. (The user agent must allow the user to indicate that the browsing context is to be closed.)
Reenable the user interface for all the browsing contexts in the list of background browsing contexts.
Return the auxiliary browsing context's return value.

The Window objects of Documents hosted by browsing contexts created by the above algorithm must all have the WindowModal interface added to their Window interface:

[Supplemental, NoInterfaceObject] interface WindowModal {
  readonly attribute any dialogArguments;
           attribute DOMString returnValue;
};

window . dialogArguments

Returns the argument argument that was passed to the showModalDialog() method.

window . returnValue [ = value ]

Returns the current return value for the window.

Can be set, to change the value that will be returned by the showModalDialog() method.

Such browsing contexts have associated dialog arguments, which are stored along with the dialog arguments' origin. These values are set by the showModalDialog() method in the algorithm above, when the browsing context is created, based on the arguments provided to the method.

The dialogArguments IDL attribute, on getting, must check whether its browsing context's active document's origin is the same as the dialog arguments' origin. If it is, then the browsing context's dialog arguments must be returned unchanged. Otherwise, if the dialog arguments are an object, then the empty string must be returned, and if the dialog arguments are not an object, then the stringification of the dialog arguments must be returned.

These browsing contexts also have an associated return value. The return value of a browsing context must be initialized to the empty string when the browsing context is created.

The returnValue IDL attribute, on getting, must return the return value of its browsing context, and on setting, must set the return value to the given new value.

The window.close() method can be used to close the browsing context.

6.4 System state and capabilities

Status: Last call for comments

The navigator attribute of the Window interface must return an instance of the Navigator interface, which represents the identity and state of the user agent (the client), and allows Web pages to register themselves as potential protocol and content handlers:

interface Navigator {
  // objects implementing this interface also implement the interfaces given below
};
Navigator implements NavigatorID;
Navigator implements NavigatorOnLine;
Navigator implements NavigatorAbilities;

[Supplemental, NoInterfaceObject]
interface NavigatorID {
  readonly attribute DOMString appName;
  readonly attribute DOMString appVersion;
  readonly attribute DOMString platform;
  readonly attribute DOMString userAgent;
};

[Supplemental, NoInterfaceObject]
interface NavigatorOnLine {
  readonly attribute boolean onLine;
};

[Supplemental, NoInterfaceObject]
interface NavigatorAbilities {
  // content handler registration
  void registerProtocolHandler(in DOMString scheme, in DOMString url, in DOMString title);
  void registerContentHandler(in DOMString mimeType, in DOMString url, in DOMString title);
  void yieldForStorageUpdates();
};

These interfaces are defined separately so that other specifications can re-use parts of the Navigator interface.

6.4.1 Client identification

Status: Last call for comments

In certain cases, despite the best efforts of the entire industry, Web browsers have bugs and limitations that Web authors are forced to work around.

This section defines a collection of attributes that can be used to determine, from script, the kind of user agent in use, in order to work around these issues.

Client detection should always be limited to detecting known current versions; future versions and unknown versions should always be assumed to be fully compliant.

window . navigator . appName: Returns the name of the browser.
window . navigator . appVersion: Returns the version of the browser.
window . navigator . platform: Returns the name of the platform.
window . navigator . userAgent: Returns the complete User-Agent header.

appName: Must return either the string "Netscape" or the full name of the browser, e.g. "Mellblom Browsernator".
appVersion: Must return either the string "4.0" or a string representing the version of the browser in detail, e.g. "1.0 (VMS; en-US) Mellblomenator/9000".
platform: Must return either the empty string or a string representing the platform on which the browser is executing, e.g. "MacIntel", "Win32", "FreeBSD i386", "WebTV OS".
userAgent: Must return the string used for the value of the "User-Agent" header in HTTP requests, or the empty string if no such header is ever sent.

6.4.2 Custom scheme and content handlers

Status: Last call for comments

The registerProtocolHandler() method allows Web sites to register themselves as possible handlers for particular schemes. For example, an online telephone messaging service could register itself as a handler of the sms: scheme ([RFC5724]), so that if the user clicks on such a link, he is given the opportunity to use that Web site. Analogously, the registerContentHandler() method allows Web sites to register themselves as possible handlers for content in a particular MIME type. For example, the same online telephone messaging service could register itself as a handler for text/directory files ([RFC2425]), so that if the user has no native application capable of handling vCards ([RFC2426]), his Web browser can instead suggest he use that site to view contact information stored on vCards that he opens.

window . navigator . registerProtocolHandler(scheme, url, title)

window . navigator . registerContentHandler(mimeType, url, title)

Registers a handler for the given scheme or content type, at the given URL, with the given title.

The string "%s" in the URL is used as a placeholder for where to put the URL of the content to be handled.

Throws a SECURITY_ERR exception if the user agent blocks the registration (this might happen if trying to register as a handler for "http", for instance).

Throws a SYNTAX_ERR if the "%s" string is missing in the URL.

User agents may, within the constraints described in this section, do whatever they like when the methods are called. A UA could, for instance, prompt the user and offer the user the opportunity to add the site to a shortlist of handlers, or make the handlers his default, or cancel the request. UAs could provide such a UI through modal UI or through a non-modal transient notification interface. UAs could also simply silently collect the information, providing it only when relevant to the user.

User agents should keep track of which sites have registered handlers (even if the user has declined such registrations) so that the user is not repeatedly prompted with the same request.

The arguments to the methods have the following meanings and corresponding implementation requirements:

protocol (registerProtocolHandler() only)

A scheme, such as ftp or sms. The scheme must be compared in an ASCII case-insensitive manner by user agents for the purposes of comparing with the scheme part of URLs that they consider against the list of registered handlers.

The scheme value, if it contains a colon (as in "ftp:"), will never match anything, since schemes don't contain colons.

This feature is not intended to be used with non-standard protocols.

mimeType (registerContentHandler() only)

A MIME type, such as model/vnd.flatland.3dml or application/vnd.google-earth.kml+xml. The MIME type must be compared in an ASCII case-insensitive manner by user agents for the purposes of comparing with MIME types of documents that they consider against the list of registered handlers.

User agents must compare the given values only to the MIME type/subtype parts of content types, not to the complete type including parameters. Thus, if mimeType values passed to this method include characters such as commas or whitespace, or include MIME parameters, then the handler being registered will never be used.

The type is compared to the MIME type used by the user agent after the sniffing algorithms have been applied.

url

A string used to build the URL of the page that will handle the requests.

When the user agent uses this URL, it must replace the first occurrence of the exact literal string "%s" with an escaped version of the absolute URL of the content in question (as defined below), then resolve the resulting URL, relative to the base URL of the entry script at the time the registerContentHandler() or registerProtocolHandler() methods were invoked, and then navigate an appropriate browsing context to the resulting URL using the GET method (or equivalent for non-HTTP URLs).

To get the escaped version of the absolute URL of the content in question, the user agent must replace every character in that absolute URL that doesn't match the <query> production defined in RFC 3986 by the percent-encoded form of that character. [RFC3986]

If the user had visited a site at http://example.com/ that made the following call:

navigator.registerContentHandler('application/x-soup', 'soup?url=%s', 'SoupWeb™')

...and then, much later, while visiting http://www.example.net/, clicked on a link such as:

<a href="chickenkïwi.soup">Download our Chicken Kïwi soup!</a>

...then, assuming this chickenkïwi.soup file was served with the MIME type application/x-soup, the UA might navigate to the following URL:

http://example.com/soup?url=http://www.example.net/chickenk%C3%AFwi.soup

This site could then fetch the chickenkïwi.soup file and do whatever it is that it does with soup (synthesize it and ship it to the user, or whatever).

title

A descriptive title of the handler, which the UA might use to remind the user what the site in question is.

User agents should raise SECURITY_ERR exceptions if the methods are called with scheme or mimeType values that the UA deems to be "privileged". For example, a site attempting to register a handler for http URLs or text/html content in a Web browser would likely cause an exception to be raised.

User agents must raise a SYNTAX_ERR exception if the url argument passed to one of these methods does not contain the exact literal string "%s", or if resolving the url argument with the first occurrence of the string "%s" removed, relative to the entry script's base URL, is not successful.

User agents must not raise any other exceptions (other than binding-specific exceptions, such as for an incorrect number of arguments in an JavaScript implementation).

This section does not define how the pages registered by these methods are used, beyond the requirements on how to process the url value (see above). To some extent, the processing model for navigating across documents defines some cases where these methods are relevant, but in general UAs may use this information wherever they would otherwise consider handing content to native plugins or helper applications.

UAs must not use registered content handlers to handle content that was returned as part of a non-GET transaction (or rather, as part of any non-idempotent transaction), as the remote site would not be able to fetch the same data.

6.4.2.1 Security and privacy

Status: Last call for comments

These mechanisms can introduce a number of concerns, in particular privacy concerns.

Hijacking all Web usage. User agents should not allow schemes that are key to its normal operation, such as http or https, to be rerouted through third-party sites. This would allow a user's activities to be trivially tracked, and would allow user information, even in secure connections, to be collected.

Hijacking defaults. It is strongly recommended that user agents do not automatically change any defaults, as this could lead the user to send data to remote hosts that the user is not expecting. New handlers registering themselves should never automatically cause those sites to be used.

Registration spamming. User agents should consider the possibility that a site will attempt to register a large number of handlers, possibly from multiple domains (e.g. by redirecting through a series of pages each on a different domain, and each registering a handler for video/mpeg — analogous practices abusing other Web browser features have been used by pornography Web sites for many years). User agents should gracefully handle such hostile attempts, protecting the user.

Misleading titles. User agents should not rely wholly on the title argument to the methods when presenting the registered handlers to the user, since sites could easily lie. For example, a site hostile.example.net could claim that it was registering the "Cuddly Bear Happy Content Handler". User agents should therefore use the handler's domain in any UI along with any title.

Hostile handler metadata. User agents should protect against typical attacks against strings embedded in their interface, for example ensuring that markup or escape characters in such strings are not executed, that null bytes are properly handled, that over-long strings do not cause crashes or buffer overruns, and so forth.

Leaking Intranet URLs. The mechanism described in this section can result in secret Intranet URLs being leaked, in the following manner:

The user registers a third-party content handler as the default handler for a content type.
The user then browses his corporate Intranet site and accesses a document that uses that content type.
The user agent contacts the third party and hands the third party the URL to the Intranet content.

No actual confidential file data is leaked in this manner, but the URLs themselves could contain confidential information. For example, the URL could be http://www.corp.example.com/upcoming-aquisitions/the-sample-company.egf, which might tell the third party that Example Corporation is intending to merge with The Sample Company. Implementors might wish to consider allowing administrators to disable this feature for certain subdomains, content types, or schemes.

Leaking secure URLs. User agents should not send HTTPS URLs to third-party sites registered as content handlers, in the same way that user agents do not send Referer (sic) HTTP headers from secure sites to third-party sites.

Leaking credentials. User agents must never send username or password information in the URLs that are escaped and included sent to the handler sites. User agents may even avoid attempting to pass to Web-based handlers the URLs of resources that are known to require authentication to access, as such sites would be unable to access the resources in question without prompting the user for credentials themselves (a practice that would require the user to know whether to trust the third-party handler, a decision many users are unable to make or even understand).

6.4.2.2 Sample user interface

Status: Last call for comments

This section is non-normative.

A simple implementation of this feature for a desktop Web browser might work as follows.

The registerContentHandler() method could display a modal dialog box:

In this dialog box, "Kittens at work" is the title of the page that invoked the method, "http://kittens.example.org/" is the URL of that page, "application/x-meowmeow" is the string that was passed to the registerContentHandler() method as its first argument (mimeType), "http://kittens.example.org/?show=%s" was the second argument (url), and "Kittens-at-work displayer" was the third argument (title).

If the user clicks the Cancel button, then nothing further happens. If the user clicks the "Trust" button, then the handler is remembered.

When the user then attempts to fetch a URL that uses the "application/x-meowmeow" MIME type, then it might display a dialog as follows:

In this dialog, the third option is the one that was primed by the site registering itself earlier.

If the user does select that option, then the browser, in accordance with the requirements described in the previous two sections, will redirect the user to "http://kittens.example.org/?show=data%3Aapplication/x-meowmeow;base64,S2l0dGVucyBhcmUgdGhlIGN1dGVzdCE%253D".

The registerProtocolHandler() method would work equivalently, but for schemes instead of unknown content types.

6.4.3 Manually releasing the storage mutex

Status: Last call for comments

window . navigator . yieldForStorageUpdates()

If a script uses the document.cookie API, or the localStorage API, the browser will block other scripts from accessing cookies or storage until the first script finishes. [WEBSTORAGE]

Calling the navigator.yieldForStorageUpdates() method tells the user agent to unblock any other scripts that may be blocked, even though the script hasn't returned.

Values of cookies and items in the Storage objects of localStorage attributes can change after calling this method, whence its name. [WEBSTORAGE]

The yieldForStorageUpdates() method, when invoked, must, if the storage mutex is owned by the event loop of the task that resulted in the method being called, release the storage mutex so that it is once again free. Otherwise, it must do nothing.

7 User interaction

This section describes various features that allow authors to enable users to edit documents and parts of documents interactively.

7.1 The `hidden` attribute

Status: Last call for comments. ISSUE-95 (hidden) blocks progress to Last Call

All HTML elements may have the hidden content attribute set. The hidden attribute is a boolean attribute. When specified on an element, it indicates that the element is not yet, or is no longer, relevant. User agents should not render elements that have the hidden attribute specified.

In the following skeletal example, the attribute is used to hide the Web game's main screen until the user logs in:

  <h1>The Example Game</h1>
  <section id="login">
   <h2>Login</h2>
   <form>
    ...
    <!-- calls login() once the user's credentials have been checked -->
   </form>
   <script>
    function login() {
      // switch screens
      document.getElementById('login').hidden = true;
      document.getElementById('game').hidden = false;
    }
   </script>
  </section>
  <section id="game" hidden>
   ...
  </section>

The hidden attribute must not be used to hide content that could legitimately be shown in another presentation. For example, it is incorrect to use hidden to hide panels in a tabbed dialog, because the tabbed interface is merely a kind of overflow presentation — showing all the form controls in one big page with a scrollbar would be equivalent, and no less correct.

Elements in a section hidden by the hidden attribute are still active, e.g. scripts and form controls in such sections still execute and submit respectively. Only their presentation to the user changes.

The hidden IDL attribute must reflect the content attribute of the same name.

7.2 Activation

Status: Last call for comments

element . click(): Acts as if the element was clicked.

Each element has a click in progress flag, initially set to false.

The click() method must run these steps:

If the element's click in progress flag is set to true, then abort these steps.
Set the click in progress flag on the element to true.
If the element has a defined activation behavior, run synthetic click activation steps on the element. Otherwise, fire a click event at the element.
Set the click in progress flag on the element to false.

7.3 Scrolling elements into view

Status: Last call for comments

element . scrollIntoView( [ top ] ): Scrolls the element into view. If the top argument is true, then the element will be scrolled to the top of the viewport, otherwise it'll be scrolled to the bottom. The default is the top.

The scrollIntoView([top]) method, when called, must cause the element on which the method was called to have the attention of the user called to it.

In a speech browser, this could happen by having the current playback position move to the start of the given element.

If the element in question cannot be brought to the user's attention, e.g. because it is hidden, or is not being rendered, then the user agent must do nothing instead.

In visual user agents, if the argument is present and has the value false, the user agent should scroll the element into view such that both the bottom and the top of the element are in the viewport, with the bottom of the element aligned with the bottom of the viewport. If it isn't possible to show the entire element in that way, or if the argument is omitted or is true, then the user agent should instead align the top of the element with the top of the viewport. If the entire scrollable part of the content is visible all at once (e.g. if a page is shorter than the viewport), then the user agent should not scroll anything. Visual user agents should further scroll horizontally as necessary to bring the element to the attention of the user.

Non-visual user agents may ignore the argument, or may treat it in some media-specific manner most useful to the user.

7.4 Focus

Status: Last call for comments

When an element is focused, key events received by the document must be targeted at that element. There may be no element focused; when no element is focused, key events received by the document must be targeted at the body element.

User agents may track focus for each browsing context or Document individually, or may support only one focused element per top-level browsing context — user agents should follow platform conventions in this regard.

Which elements within a top-level browsing context currently have focus must be independent of whether or not the top-level browsing context itself has the system focus.

When an element is focused, the element matches the CSS :focus pseudo-class.

Status: Last call for comments

The tabindex content attribute specifies whether the element is focusable, whether it can be reached using sequential focus navigation, and the relative order of the element for the purposes of sequential focus navigation. The name "tab index" comes from the common use of the "tab" key to navigate through the focusable elements. The term "tabbing" refers to moving forward through the focusable elements that can be reached using sequential focus navigation.

The tabindex attribute, if specified, must have a value that is a valid integer.

If the attribute is specified, it must be parsed using the rules for parsing integers. The attribute's values have the following meanings:

If the attribute is omitted or parsing the value returns an error

The user agent should follow platform conventions to determine if the element is to be focusable and, if so, whether the element can be reached using sequential focus navigation, and if so, what its relative order should be.

If the value is a negative integer

The user agent must allow the element to be focused, but should not allow the element to be reached using sequential focus navigation.

If the value is a zero

The user agent must allow the element to be focused, should allow the element to be reached using sequential focus navigation, and should follow platform conventions to determine the element's relative order.

If the value is greater than zero

The user agent must allow the element to be focused, should allow the element to be reached using sequential focus navigation, and should place the element in the sequential focus navigation order so that it is:

before any focusable element whose tabindex attribute has been omitted or whose value, when parsed, returns an error,
before any focusable element whose tabindex attribute has a value equal to or less than zero,
after any element whose tabindex attribute has a value greater than zero but less than the value of the tabindex attribute on the element,
after any element whose tabindex attribute has a value equal to the value of the tabindex attribute on the element but that is earlier in the document in tree order than the element,
before any element whose tabindex attribute has a value equal to the value of the tabindex attribute on the element but that is later in the document in tree order than the element, and
before any element whose tabindex attribute has a value greater than the value of the tabindex attribute on the element.

An element is specially focusable if the tabindex attribute's definition above defines the element to be focusable.

An element that is specially focusable but does not otherwise have an activation behavior defined has an activation behavior that does nothing.

This means that an element that is only focusable because of its tabindex attribute will fire a click event in response to a non-mouse activation (e.g. hitting the "enter" key while the element is focused).

The tabIndex IDL attribute must reflect the value of the tabindex content attribute. If the attribute is not present, or parsing its value returns an error, then the IDL attribute must return 0 for elements that are focusable and −1 for elements that are not focusable.

7.4.2 Focus management

Status: Last call for comments

An element is focusable if the user agent's default behavior allows it to be focusable or if the element is specially focusable, but only if the element is either being rendered or is a descendant of a canvas element that represents embedded content.

User agents should make the following elements focusable, unless platform conventions dictate otherwise:

a elements that have an href attribute
link elements that have an href attribute
button elements that are not disabled
input elements whose type attribute are not in the Hidden state and that are not disabled
select elements that are not disabled
textarea elements that are not disabled
command elements that do not have a disabled attribute
Elements with a draggable attribute set, if that would enable the user agent to allow the user to begin a drag operations for those elements without the use of a pointing device

In addition, each shape that is generated for an area element should be focusable, unless platform conventions dictate otherwise. (A single area element can correspond to multiple shapes, since image maps can be reused with multiple images on a page.)

The focusing steps are as follows:

If focusing the element will remove the focus from another element, then run the unfocusing steps for that element.
Make the element the currently focused element in its top-level browsing context.

Some elements, most notably area, can correspond to more than one distinct focusable area. If a particular area was indicated when the element was focused, then that is the area that must get focus; otherwise, e.g. when using the focus() method, the first such region in tree order is the one that must be focused.
Fire a simple event named focus at the element.

User agents must synchronously run the focusing steps for an element whenever the user moves the focus to a focusable element.

The unfocusing steps are as follows:

If the element is an input element, and the change event applies to the element, and the element does not have a defined activation behavior, and the user has changed the element's value or its list of selected files while the control was focused without committing that change, then fire a simple event that bubbles named change at the element, then broadcast formchange events at the element's form owner.
Unfocus the element.
Fire a simple event named blur at the element.

When an element that is focused stops being a focusable element, or stops being focused without another element being explicitly focused in its stead, the user agent should synchronously run the focusing steps for the body element, if there is one; if there is not, then the user agent should synchronously run the unfocusing steps for the affected element only.

For example, this might happen because the element is removed from its Document, or has a hidden attribute added. It would also happen to an input element when the element gets disabled.

7.4.3 Document-level focus APIs

Status: Last call for comments

document . activeElement: Returns the currently focused element.
document . hasFocus(): Returns true if the document has focus; otherwise, returns false.
window . focus(): Focuses the window. Use of this method is discouraged. Allow the user to control window focus instead.
window . blur(): Unfocuses the window. Use of this method is discouraged. Allow the user to control window focus instead.

The activeElement attribute on HTMLDocument objects must return the element in the document that is focused. If no element in the Document is focused, this must return the body element.

The hasFocus() method on HTMLDocument objects must return true if the document's browsing context is focused, and all its ancestor browsing contexts are also focused, and the top-level browsing context has the system focus.

The focus() method on the Window object, when invoked, provides a hint to the user agent that the script believes the user might be interested in the contents of the browsing context of the Window object on which the method was invoked.

User agents are encouraged to have this focus() method trigger some kind of notification.

The blur() method on the Window object, when invoked, provides a hint to the user agent that the script believes the user probably is not currently interested in the contents of the browsing context of the Window object on which the method was invoked, but that the contents might become interesting again in the future.

User agents are encouraged to ignore calls to this blur() method entirely.

Historically the focus() and blur() methods actually affected the system focus, but hostile sites widely abuse this behavior to the user's detriment.

7.4.4 Element-level focus APIs

Status: Last call for comments

element . focus()

Focuses the element.

element . blur()

Unfocuses the element. Use of this method is discouraged. Focus another element instead.

Do not use this method to hide the focus ring if you find the focus ring unsightly. Instead, use a CSS rule to override the 'outline' property.

For example, to hide the outline from links, you could use:

:link:focus, :visited:focus { outline: none; }

The focus() method, when invoked, must run the following algorithm:

If the element is marked as locked for focus, then abort these steps.
If the element is not focusable, then abort these steps.
Mark the element as locked for focus.
If the element is not already focused, run the focusing steps for the element.
Unmark the element as locked for focus.

The blur() method, when invoked, should run the focusing steps for the body element, if there is one; if there is not, then it should run the unfocusing steps for the element on which the method was called instead. User agents may selectively or uniformly ignore calls to this method for usability reasons.

For example, if the blur() method is unwisely being used to remove the focus ring for aesthetics reasons, the page would become unusable by keyboard users. Ignoring calls to this method would thus allow keyboard users to interact with the page.

7.5 The `accesskey` attribute

Status: Last call for comments

All HTML elements may have the accesskey content attribute set. The accesskey attribute's value is used by the user agent as a guide for creating a keyboard shortcut that activates or focuses the element.

If specified, the value must be an ordered set of unique space-separated tokens, each of which must be exactly one Unicode code point in length.

An element's assigned access key is a key combination derived from the element's accesskey content attribute as follows:

If the element has no accesskey attribute, then skip to the fallback step below.
Otherwise, the user agent must split the attribute's value on spaces, and let keys be the resulting tokens.
For each value in keys in turn, in the order the tokens appeared in the attribute's value, run the following substeps:
1. If the value is not a string exactly one Unicode code point in length, then skip the remainder of these steps for this value.
2. If the value does not correspond to a key on the system's keyboard, then skip the remainder of these steps for this value.
3. If the user agent can find a combination of modifier keys that, with the key that corresponds to the value given in the attribute, can be used as a shortcut key, then the user agent may assign that combination of keys as the element's assigned access key and abort these steps.
Fallback: Optionally, the user agent may assign a key combination of its choosing as the element's assigned access key and then abort these steps.
If this step is reached, the element has no assigned access key.

Once a user agent has selected and assigned an access key for an element, the user agent should not change the element's assigned access key unless the accesskey content attribute is changed or the element is moved to another Document.

When the user presses the key combination corresponding to the assigned access key for an element, if the element defines a command, and the command's Hidden State facet is false (visible), and the command's Disabled State facet is also false (enabled), then the user agent must trigger the Action of the command.

User agents may expose elements that have an accesskey attribute in other ways as well, e.g. in a menu displayed in response to a specific key combination.

The accessKey IDL attribute must reflect the accesskey content attribute.

The accessKeyLabel IDL attribute must return a string that represents the element's assigned access key, if any. If the element does not have one, then the IDL attribute must return the empty string.

In the following example, a variety of links are given with access keys so that keyboard users familiar with the site can more quickly navigate to the relevant pages:

<nav>
 <p>
  <a title="Consortium Activities" accesskey="A" href="/Consortium/activities">Activities</a> |
  <a title="Technical Reports and Recommendations" accesskey="T" href="/TR/">Technical Reports</a> |
  <a title="Alphabetical Site Index" accesskey="S" href="/Consortium/siteindex">Site Index</a> |
  <a title="About This Site" accesskey="B" href="/Consortium/">About Consortium</a> |
  <a title="Contact Consortium" accesskey="C" href="/Consortium/contact">Contact</a>
 </p>
</nav>

In the following example, the search field is given two possible access keys, "s" and "0" (in that order). A user agent on a device with a full keyboard might pick Ctrl+Alt+S as the shortcut key, while a user agent on a small device with just a numeric keypad might pick just the plain unadorned key 0:

<form action="/search">
 <label>Search: <input type="search" name="q" accesskey="s 0"></label>
 <input type="submit">
</form>

In the following example, a button has possible access keys described. A script then tries to update the button's label to advertise the key combination the user agent selected.

<input type=submit accesskey="N @ 1" value="Compose">
...
<script>
 function labelButton(button) {
   if (button.accessKeyLabel)
     button.value += ' (' + button.accessKeyLabel + ')';
 }
 var inputs = document.getElementsByTagName('input');
 for (var i = 0; i < inputs.length; i += 1) {
   if (inputs[i].type == "submit")
     labelButton(inputs[i]);
 }
</script>

On one user agent, the button's label might become "Compose (⌘N)". On another, it might become "Compose (Alt+⇧+1)". If the user agent doesn't assign a key, it will be just "Compose". The exact string depends on what the assigned access key is, and on how the user agent represents that key combination.

7.6 The text selection APIs

Status: Last call for comments

Every browsing context has a selection. The selection can be empty, and the selection can have more than one range (a disjointed selection). The user agent should allow the user to change the selection. User agents are not required to let the user select more than one range, and may collapse multiple ranges in the selection to a single range when the user interacts with the selection. (But, of course, the user agent may let the user create selections with multiple ranges.)

This one selection must be shared by all the content of the browsing context (though not by nested browsing contexts), including any editing hosts in the document. (Editing hosts that are not inside a document cannot have a selection.)

If the selection is empty (collapsed, so that it has only one segment and that segment's start and end points are the same) then the selection's position should equal the caret position. When the selection is not empty, this specification does not define the caret position; user agents should follow platform conventions in deciding whether the caret is at the start of the selection, the end of the selection, or somewhere else.

On some platforms (such as those using Wordstar editing conventions), the caret position is totally independent of the start and end of the selection, even when the selection is empty. On such platforms, user agents may ignore the requirement that the cursor position be linked to the position of the selection altogether.

Mostly for historical reasons, in addition to the browsing context's selection, each textarea and input element has an independent selection. These are the text field selections.

User agents may selectively ignore attempts to use the API to adjust the selection made after the user has modified the selection. For example, if the user has just selected part of a word, the user agent could ignore attempts to use the API call to immediately unselect the selection altogether, but could allow attempts to change the selection to select the entire word.

User agents may also allow the user to create selections that are not exposed to the API.

The select element also has a selection, indicating which items have been picked by the user. This is not discussed in this section.

This specification does not specify how selections are presented to the user.

7.6.1 APIs for the browsing context selection

Status: Last call for comments

window . getSelection()
document . getSelection(): Returns the Selection object for the window, which stringifies to the text of the current selection.

The getSelection() method on the Window interface must return the Selection object representing the selection of that Window object's browsing context.

For historical reasons, the getSelection() method on the HTMLDocument interface must return the same Selection object.

interface Selection {
  readonly attribute Node anchorNode;
  readonly attribute long anchorOffset;
  readonly attribute Node focusNode;
  readonly attribute long focusOffset;
  readonly attribute boolean isCollapsed;
  void collapse(in Node parentNode, in long offset);
  void collapseToStart();
  void collapseToEnd();
  void selectAllChildren(in Node parentNode);
  void deleteFromDocument();
  readonly attribute long rangeCount;
  Range getRangeAt(in long index);
  void addRange(in Range range);
  void removeRange(in Range range);
  void removeAllRanges();
  stringifier DOMString ();
};

The Selection interface represents a list of Range objects. The first item in the list has index 0, and the last item has index count-1, where count is the number of ranges in the list. [DOMRANGE]

All of the members of the Selection interface are defined in terms of operations on the Range objects represented by this object. These operations can raise exceptions, as defined for the Range interface; this can therefore result in the members of the Selection interface raising exceptions as well, in addition to any explicitly called out below.

selection . anchorNode

Returns the element that contains the start of the selection.

Returns null if there's no selection.

selection . anchorOffset

Returns the offset of the start of the selection relative to the element that contains the start of the selection.

Returns 0 if there's no selection.

selection . focusNode

Returns the element that contains the end of the selection.

Returns null if there's no selection.

selection . focusOffset

Returns the offset of the end of the selection relative to the element that contains the end of the selection.

Returns 0 if there's no selection.

collapsed = selection . isCollapsed()

Returns true if there's no selection or if the selection is empty. Otherwise, returns false.

selection . collapsed(parentNode, offset)

Replaces the selection with an empty one at the given position.

Throws a WRONG_DOCUMENT_ERR exception if the given node is in a different document.

selection . collapseToStart()

Replaces the selection with an empty one at the position of the start of the current selection.

Throws an INVALID_STATE_ERR exception if there is no selection.

selection . collapseToEnd()

Replaces the selection with an empty one at the position of the end of the current selection.

Throws an INVALID_STATE_ERR exception if there is no selection.

selection . selectAllChildren(parentNode)

Replaces the selection with one that contains all the contents of the given element.

Throws a WRONG_DOCUMENT_ERR exception if the given node is in a different document.

selection . deleteFromDocument()

Deletes the selection.

selection . rangeCount

Returns the number of ranges in the selection.

selection . getRangeAt(index)

Returns the given range.

Throws an INVALID_STATE_ERR exception if the value is out of range.

selection . addRange(range)

Adds the given range to the selection.

selection . removeRange(range)

Removes the given range from the selection, if the range was one of the ones in the selection.

selection . removeAllRanges()

Removes all the ranges in the selection.

The anchorNode attribute must return the value returned by the startContainer attribute of the last Range object in the list, or null if the list is empty.

The anchorOffset attribute must return the value returned by the startOffset attribute of the last Range object in the list, or 0 if the list is empty.

The focusNode attribute must return the value returned by the endContainer attribute of the last Range object in the list, or null if the list is empty.

The focusOffset attribute must return the value returned by the endOffset attribute of the last Range object in the list, or 0 if the list is empty.

The isCollapsed attribute must return true if there are zero ranges, or if there is exactly one range and its collapsed attribute is itself true. Otherwise it must return false.

The collapse(parentNode, offset) method must raise a WRONG_DOCUMENT_ERR DOM exception if parentNode's Document is not the HTMLDocument object with which the Selection object is associated. Otherwise it is, and the method must remove all the ranges in the Selection list, then create a new Range object, add it to the list, and invoke its setStart() and setEnd() methods with the parentNode and offset values as their arguments.

The collapseToStart() method must raise an INVALID_STATE_ERR DOM exception if there are no ranges in the list. Otherwise, it must invoke the collapse() method with the startContainer and startOffset values of the first Range object in the list as the arguments.

The collapseToEnd() method must raise an INVALID_STATE_ERR DOM exception if there are no ranges in the list. Otherwise, it must invoke the collapse() method with the endContainer and endOffset values of the last Range object in the list as the arguments.

The selectAllChildren(parentNode) method must invoke the collapse() method with the parentNode value as the first argument and 0 as the second argument, and must then invoke the selectNodeContents() method on the first (and only) range in the list with the parentNode value as the argument.

The deleteFromDocument() method must invoke the deleteContents() method on each range in the list, if any, from first to last.

The rangeCount attribute must return the number of ranges in the list.

The getRangeAt(index) method must return the indexth range in the list. If index is less than zero or greater or equal to the value returned by the rangeCount attribute, then the method must raise an INDEX_SIZE_ERR DOM exception.

The addRange(range) method must add the given range Range object to the list of selections, at the end (so the newly added range is the new last range). Duplicates are not prevented; a range may be added more than once in which case it appears in the list more than once, which (for example) will cause stringification to return the range's text twice.

The removeRange(range) method must remove the first occurrence of range in the list of ranges, if it appears at all.

The removeAllRanges() method must remove all the ranges from the list of ranges, such that the rangeCount attribute returns 0 after the removeAllRanges() method is invoked (and until a new range is added to the list, either through this interface or via user interaction).

Objects implementing this interface must stringify to a concatenation of the results of invoking the toString() method of the Range object on each of the ranges of the selection, in the order they appear in the list (first to last).

In the following document fragment, the emphasized parts indicate the selection.

<p>The cute girl likes the <cite>Oxford English Dictionary</cite>.</p>

If a script invoked window.getSelection().toString(), the return value would be "the Oxford English".

7.6.2 APIs for the text field selections

Status: Last call for comments

The input and textarea elements define the following members in their DOM interfaces for handling their text selection:

  void select();
           attribute unsigned long selectionStart;
           attribute unsigned long selectionEnd;
  void setSelectionRange(in unsigned long start, in unsigned long end);

These methods and attributes expose and control the selection of input and textarea text fields.

element . select()

Selects everything in the text field.

element . selectionStart [ = value ]

Returns the offset to the start of the selection.

Can be set, to change the start of the selection.

element . selectionEnd [ = value ]

Returns the offset to the end of the selection.

Can be set, to change the end of the selection.

element . setSelectionRange(start, end)

Changes the selection to cover the given substring.

When these methods and attributes are used with input elements while they don't apply, they must raise an INVALID_STATE_ERR exception. Otherwise, they must act as described below.

The select() method must cause the contents of the text field to be fully selected.

The selectionStart attribute must, on getting, return the offset (in logical order) to the character that immediately follows the start of the selection. If there is no selection, then it must return the offset (in logical order) to the character that immediately follows the text entry cursor.

On setting, it must act as if the setSelectionRange() method had been called, with the new value as the first argument, and the current value of the selectionEnd attribute as the second argument, unless the current value of the selectionEnd is less than the new value, in which case the second argument must also be the new value.

The selectionEnd attribute must, on getting, return the offset (in logical order) to the character that immediately follows the end of the selection. If there is no selection, then it must return the offset (in logical order) to the character that immediately follows the text entry cursor.

On setting, it must act as if the setSelectionRange() method had been called, with the current value of the selectionStart attribute as the first argument, and new value as the second argument.

The setSelectionRange(start, end) method must set the selection of the text field to the sequence of characters starting with the character at the startth position (in logical order) and ending with the character at the (end-1)th position. Arguments greater than the length of the value in the text field must be treated as pointing at the end of the text field. If end is less than or equal to start then the start of the selection and the end of the selection must both be placed immediately before the character with offset end. In UAs where there is no concept of an empty selection, this must set the cursor to be just before the character with offset end.

To obtain the currently selected text, the following JavaScript suffices:

var selectionText = control.value.substring(control.selectionStart, control.selectionEnd);

...where control is the input or textarea element.

Characters with no visible rendering, such as U+200D ZERO WIDTH JOINER, still count as characters. Thus, for instance, the selection can include just an invisible character, and the text insertion cursor can be placed to one side or another of such a character.

7.7 The `contenteditable` attribute

Status: Last call for comments

The contenteditable attribute is an enumerated attribute whose keywords are the empty string, true, and false. The empty string and the true keyword map to the true state. The false keyword maps to the false state. In addition, there is a third state, the inherit state, which is the missing value default (and the invalid value default).

The true state indicates that the element is editable. The inherit state indicates that the element is editable if its parent is. The false state indicates that the element is not editable.

Specifically, if an HTML element has a contenteditable attribute set to the true state, or it has its contenteditable attribute set to the inherit state and if its nearest ancestor HTML element with the contenteditable attribute set to a state other than the inherit state has its attribute set to the true state, or if it and its ancestors all have their contenteditable attribute set to the inherit state but the Document has designMode enabled, then the UA must treat the element as editable (as described below).

Otherwise, either the HTML element has a contenteditable attribute set to the false state, or its contenteditable attribute is set to the inherit state and its nearest ancestor HTML element with the contenteditable attribute set to a state other than the inherit state has its attribute set to the false state, or all its ancestors have their contenteditable attribute set to the inherit state and the Document itself has designMode disabled; either way, the element is not editable.

element . contentEditable [ = value ]

Returns "true", "false", or "inherit", based on the state of the contenteditable attribute.

Can be set, to change that state.

Throws a SYNTAX_ERR exception if the new value isn't one of those strings.

element . isContentEditable

Returns true if the element is editable; otherwise, returns false.

The contentEditable IDL attribute, on getting, must return the string "true" if the content attribute is set to the true state, false" if the content attribute is set to the false state, and "inherit" otherwise. On setting, if the new value is an ASCII case-insensitive match for the string "inherit" then the content attribute must be removed, if the new value is an ASCII case-insensitive match for the string "true" then the content attribute must be set to the string "true", if the new value is an ASCII case-insensitive match for the string "false" then the content attribute must be set to the string "false", and otherwise the attribute setter must raise a SYNTAX_ERR exception.

The isContentEditable IDL attribute, on getting, must return true if the element is editable, and false otherwise.

If an element is editable and its parent element is not, or if an element is editable and it has no parent element, then the element is an editing host. Editable elements can be nested. User agents must make editing hosts focusable (which typically means they enter the tab order). An editing host can contain non-editable sections, these are handled as described below. An editing host can contain non-editable sections that contain further editing hosts.

When an editing host has focus, it must have a caret position that specifies where the current editing position is. It may also have a selection.

How the caret and selection are represented depends entirely on the UA.

7.7.1 User editing actions

Status: Last call for comments

There are several actions that the user agent should allow the user to perform while the user is interacting with an editing host. How exactly each action is triggered is not defined for every action, but when it is not defined, suggested key bindings are provided to guide implementors.

Move the caret

User agents must allow users to move the caret to any position within an editing host, even into nested editable elements. This could be triggered as the default action of keydown events with various key identifiers and as the default action of mousedown events.

Change the selection

User agents must allow users to change the selection within an editing host, even into nested editable elements. User agents may prevent selections from being made in ways that cross from editable elements into non-editable elements (e.g. by making each non-editable descendant atomically selectable, but not allowing text selection within them). This could be triggered as the default action of keydown events with various key identifiers and as the default action of mousedown events.

Insert text

This action must be triggered as the default action of a textInput event, and may be triggered by other commands as well. It must cause the user agent to insert the specified text (given by the event object's data attribute in the case of the textInput event) at the caret.

If the caret is positioned somewhere where phrasing content is not allowed (e.g. inside an empty ol element), then the user agent must not insert the text directly at the caret position. In such cases the behavior is UA-dependent, but user agents must not, in response to a request to insert text, generate a DOM that is less conformant than the DOM prior to the request.

User agents should allow users to insert new paragraphs into elements that contains only content other than paragraphs.

For example, given the markup:

<section>
 <dl>
  <dt> Ben </dt>
  <dd> Goat </dd>
 </dl>
</section>

...the user agent should allow the user to insert p elements before and after the dl element, as children of the section element.

Break block

UAs should offer a way for the user to request that the current paragraph be broken at the caret, e.g. as the default action of a keydown event whose identifier is the "Enter" key and that has no modifiers set.

The exact behavior is UA-dependent, but user agents must not, in response to a request to break a paragraph, generate a DOM that is less conformant than the DOM prior to the request.

Insert a line separator

UAs should offer a way for the user to request an explicit line break at the caret position without breaking the paragraph, e.g. as the default action of a keydown event whose identifier is the "Enter" key and that has a shift modifier set. Line separators are typically found within a poem verse or an address. To insert a line break, the user agent must insert a br element.

If the caret is positioned somewhere where phrasing content is not allowed (e.g. in an empty ol element), then the user agent must not insert the br element directly at the caret position. In such cases the behavior is UA-dependent, but user agents must not, in response to a request to insert a line separator, generate a DOM that is less conformant than the DOM prior to the request.

Delete

UAs should offer a way for the user to delete text and elements, including non-editable descendants, e.g. as the default action of keydown events whose identifiers are "U+0008" or "U+007F".

Five edge cases in particular need to be considered carefully when implementing this feature: backspacing at the start of an element, backspacing when the caret is immediately after an element, forward-deleting at the end of an element, forward-deleting when the caret is immediately before an element, and deleting a selection whose start and end points do not share a common parent node.

In any case, the exact behavior is UA-dependent, but user agents must not, in response to a request to delete text or an element, generate a DOM that is less conformant than the DOM prior to the request.

Insert, and wrap text in, semantic elements

UAs should offer the user the ability to mark text and paragraphs with semantics that HTML can express.

UAs should similarly offer a way for the user to insert empty semantic elements to subsequently fill by entering text manually.

UAs should also offer a way to remove those semantics from marked up text, and to remove empty semantic element that have been inserted.

In response to a request from a user to mark text up in italics, user agents should use the i element to represent the semantic. The em element should be used only if the user agent is sure that the user means to indicate stress emphasis.

In response to a request from a user to mark text up in bold, user agents should use the b element to represent the semantic. The strong element should be used only if the user agent is sure that the user means to indicate importance.

The exact behavior is UA-dependent, but user agents must not, in response to a request to wrap semantics around some text or to insert or remove a semantic element, generate a DOM that is less conformant than the DOM prior to the request.

Select and move non-editable elements nested inside editing hosts

UAs should offer a way for the user to move images and other non-editable parts around the content within an editing host. This may be done using the drag and drop mechanism. User agents must not, in response to a request to move non-editable elements nested inside editing hosts, generate a DOM that is less conformant than the DOM prior to the request.

Edit form controls nested inside editing hosts

When an editable form control is edited, the changes must be reflected in both its current value and its default value. For input elements this means updating the defaultValue IDL attribute as well as the value IDL attribute; for select elements it means updating the option elements' defaultSelected IDL attribute as well as the selected IDL attribute; for textarea elements this means updating the defaultValue IDL attribute as well as the value IDL attribute. (Updating the default* IDL attributes causes content attributes to be updated as well.)

User agents may perform several commands per user request; for example if the user selects a block of text and hits Enter, the UA might interpret that as a request to delete the content of the selection followed by a request to break the paragraph at that position.

User agents may add DOM changes entries to the undo transaction history of the editing host's Document object each time an action is triggered.

All of the actions defined above, whether triggered by the user or programmatically (e.g. by execCommand() commands), must fire mutation events as appropriate.

7.7.2 Making entire documents editable

Status: Last call for comments

Documents have a designMode, which can be either enabled or disabled.

document . designMode [ = value ]

Returns "on" if the document is editable, and "off" if it isn't.

Can be set, to change the document's current state.

The designMode IDL attribute on the Document object takes two values, "on" and "off". When it is set, the new value must be compared in an ASCII case-insensitive manner to these two values. If it matches the "on" value, then designMode must be enabled, and if it matches the "off" value, then designMode must be disabled. Other values must be ignored.

When designMode is enabled, the IDL attribute must return the value "on", and when it is disabled, it must return the value "off".

The last state set must persist until the document is destroyed or the state is changed. Initially, documents must have their designMode disabled.

7.8 Spelling and grammar checking

Status: Last call for comments

User agents can support the checking of spelling and grammar of editable text, either in form controls (such as the value of textarea elements), or in elements in an editing host (using contenteditable).

For each element, user agents must establish a default behavior, either through defaults or through preferences expressed by the user. There are three possible default behaviors for each element:

true-by-default: The element will be checked for spelling and grammar if its contents are editable.
false-by-default: The element will never be checked for spelling and grammar.
inherit-by-default: The element's default behavior is the same as its parent element's. Elements that have no parent element cannot have this as their default behavior.

The spellcheck attribute is an enumerated attribute whose keywords are the empty string, true and false. The empty string and the true keyword map to the true state. The false keyword maps to the false state. In addition, there is a third state, the default state, which is the missing value default (and the invalid value default).

The true state indicates that the element is to have its spelling and grammar checked. The default state indicates that the element is to act according to a default behavior, possibly based on the parent element's own spellcheck state. The false state indicates that the element is not to be checked.

element . spellcheck [ = value ]

Returns "true", "false", or "default", based on the state of the spellcheck attribute.

Can be set, to change that state.

Throws a SYNTAX_ERR exception if the new value isn't one of those strings.

The spellcheck IDL attribute, on getting, must return the string "true" if the content attribute is set to the true state, false" if the content attribute is set to the false state, and "default" otherwise. On setting, if the new value is an ASCII case-insensitive match for the string "default" then the content attribute must be removed, if the new value is an ASCII case-insensitive match for the string "true" then the content attribute must be set to the string "true", if the new value is an ASCII case-insensitive match for the string "false" then the content attribute must be set to the string "false", and otherwise the attribute setter must raise a SYNTAX_ERR exception.

The spellcheck IDL attribute is not affected by user preferences that override the spellcheck content attribute, and therefore might not reflect the actual spellchecking state.

On setting, if the new value is true, then the element's spellcheck content attribute must be set to the literal string "true", otherwise it must be set to the literal string "false".

User agents must only consider the following pieces of text as checkable for the purposes of this feature:

The value of input elements to which the readonly attribute applies, whose type attributes are not in the Password state, and that are not immutable (i.e. that do not have the readonly attribute specified and that are not disabled).
The value of textarea elements that do not have a readonly attribute and that are not disabled.
Text in text nodes that are children of editable elements.
Text in attributes of editable elements.

For text that is part of a text node, the element with which the text is associated is the element that is the immediate parent of the first character of the word, sentence, or other piece of text. For text in attributes, it is the attribute's element. For the values of input and textarea elements, it is the element itself.

To determine if a word, sentence, or other piece of text in an applicable element (as defined above) is to have spelling- and/or grammar-checking enabled, the UA must use the following algorithm:

If the user has disabled the checking for this text, then the checking is disabled.
Otherwise, if the user has forced the checking for this text to always be enabled, then the checking is enabled.
Otherwise, if the element with which the text is associated has a spellcheck content attribute, then: if that attribute is in the true state, then checking is enabled; otherwise, if that attribute is in the false state, then checking is disabled.
Otherwise, if there is an ancestor element with a spellcheck content attribute that is not in the default state, then: if the nearest such ancestor's spellcheck content attribute is in the true state, then checking is enabled; otherwise, checking is disabled.
Otherwise, if the element's default behavior is true-by-default, then checking is enabled.
Otherwise, if the element's default behavior is false-by-default, then checking is disabled.
Otherwise, if the element's parent element has its checking enabled, then checking is enabled.
Otherwise, checking is disabled.

If the checking is enabled for a word/sentence/text, the user agent should indicate spelling and/or grammar errors in that text. User agents should take into account the other semantics given in the document when suggesting spelling and grammar corrections. User agents may use the language of the element to determine what spelling and grammar rules to use, or may use the user's preferred language settings. UAs should use input element attributes such as pattern to ensure that the resulting value is valid, where possible.

If checking is disabled, the user agent should not indicate spelling or grammar errors for that text.

The element with ID "a" in the following example would be the one used to determine if the word "Hello" is checked for spelling errors. In this example, it would not be.

<div contenteditable="true">
 <span spellcheck="false" id="a">Hell</span><em>o!</em>
</div>

The element with ID "b" in the following example would have checking enabled (the leading space character in the attribute's value on the input element causes the attribute to be ignored, so the ancestor's value is used instead, regardless of the default).

<p spellcheck="true">
 <label>Name: <input spellcheck=" false" id="b"></label>
</p>

This specification does not define the user interface for spelling and grammar checkers. A user agent could offer on-demand checking, could perform continuous checking while the checking is enabled, or could use other interfaces.

7.9 Drag and drop

Status: Last call for comments

This section defines an event-based drag-and-drop mechanism.

This specification does not define exactly what a drag-and-drop operation actually is.

On a visual medium with a pointing device, a drag operation could be the default action of a mousedown event that is followed by a series of mousemove events, and the drop could be triggered by the mouse being released.

On media without a pointing device, the user would probably have to explicitly indicate his intention to perform a drag-and-drop operation, stating what he wishes to drag and what he wishes to drop, respectively.

However it is implemented, drag-and-drop operations must have a starting point (e.g. where the mouse was clicked, or the start of the selection or element that was selected for the drag), may have any number of intermediate steps (elements that the mouse moves over during a drag, or elements that the user picks as possible drop points as he cycles through possibilities), and must either have an end point (the element above which the mouse button was released, or the element that was finally selected), or be canceled. The end point must be the last element selected as a possible drop point before the drop occurs (so if the operation is not canceled, there must be at least one element in the middle step).

7.9.1 Introduction

Status: Last call for comments

This section is non-normative.

To make an element draggable is simple: give the element a draggable attribute, and set an event listener for dragstart that stores the data being dragged.

The event handler typically needs to check that it's not a text selection that is being dragged, and then needs to store data into the DataTransfer object and set the allowed effects (copy, move, link, or some combination).

For example:

<p>What fruits do you like?</p>
<ol ondragstart="dragStartHandler(event)">
 <li draggable data-value="fruit-apple">Apples</li>
 <li draggable data-value="fruit-orange">Oranges</li>
 <li draggable data-value="fruit-pear">Pears</li>
</ol>
<script>
  var internalDNDType = 'text/x-example'; // set this to something specific to your site
  function dragStartHandler(event) {
    if (event.target instanceof HTMLLIElement) {
      // use the element's data-value="" attribute as the value to be moving:
      event.dataTransfer.setData(internalDNDType, event.target.dataset.value);
      event.effectAllowed = 'move'; // only allow moves
    } else {
      event.preventDefault(); // don't allow selection to be dragged
    }
  }
</script>

To accept a drop, the drop target has to listen to at least three events. First, the dragenter event, which is used to determine whether or not the drop target is to accept the drop. If the drop is to be accepted, then this event has to be canceled. Second, the dragover event, which is used to determine what feedback is to be shown to the user. If the event is canceled, then the feedback (typically the cursor) is updated based on the dropEffect attribute's value, as set by the event handler; otherwise, the default behavior (typically to do nothing) is used instead. Finally, the drop event, which allows the actual drop to be performed. This event also needs to be canceled, so that the dropEffect attribute's value can be used by the source (otherwise it's reset).

For example:

<p>Drop your favourite fruits below:</p>
<ol class="dropzone"
    ondragenter="dragEnterHandler(event)"
    ondragover="dragOverHandler(event)"
    ondrop="dropHandler(event)">
</ol>
<script>
  var internalDNDType = 'text/x-example'; // set this to something specific to your site
  function dragEnterHandler(event) {
    // cancel the event if the drag contains data of our type
    if (event.dataTransfer.types.contains(internalDNDType))
      event.preventDefault();
  }
  function dragOverHandler(event) {
    event.dataTransfer.dropEffect = 'move';
    event.preventDefault();
  }
  function dropHandler(event) {
    // drop the data
    var li = document.createElement('li');
    var data = event.dataTransfer.getData(internalDNDType);
    if (data == 'fruit-apple') {
      li.textContent = 'Apples';
    } else if (data == 'fruit-orange') {
      li.textContent = 'Oranges';
    } else if (data == 'fruit-pear') {
      li.textContent = 'Pears';
    } else {
      li.textContent = 'Unknown Fruit';
    }
    event.target.appendChild(li);
  }
</script>

To remove the original element (the one that was dragged) from the display, the dragend event can be used.

For our example here, that means updating the original markup to handle that event:

<p>What fruits do you like?</p>
<ol ondragstart="dragStartHandler(event)" ondragend="dragEndHandler(event)">
 ...as before...
</ol>
<script>
  function dragStartHandler(event) {
    // ...as before...
  }
  function dragEndHandler(event) {
    // remove the dragged element
    event.target.parentNode.removeChild(event.target);
  }
</script>

7.9.2 The `DragEvent` and `DataTransfer` interfaces

Status: Last call for comments

The drag-and-drop processing model involves several events. They all use the DragEvent interface.

interface DragEvent : MouseEvent {
  readonly attribute DataTransfer dataTransfer;

  void initDragEvent(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in AbstractView viewArg, in long detailArg, in long screenXArg, in long screenYArg, in long clientXArg, in long clientYArg, in boolean ctrlKeyArg, in boolean altKeyArg, in boolean shiftKeyArg, in boolean metaKeyArg, in unsigned short buttonArg, in EventTarget relatedTargetArg, in DataTransfer dataTransferArg);
};

event . dataTransfer: Returns the DataTransfer object for the event.

The initDragEvent() method must initialize the event in a manner analogous to the similarly-named method in the DOM Events interfaces. [DOMEVENTS]

The dataTransfer attribute of the DragEvent interface represents the context information for the event.

interface DataTransfer {
           attribute DOMString dropEffect;
           attribute DOMString effectAllowed;

  readonly attribute DOMStringList types;
  void clearData(in optional DOMString format);
  void setData(in DOMString format, in DOMString data);
  DOMString getData(in DOMString format);
  readonly attribute FileList files;

  void setDragImage(in Element image, in long x, in long y);
  void addElement(in Element element);
};

DataTransfer objects can hold pieces of data, each associated with a unique format. Formats are generally given by MIME types, with some values special-cased for legacy reasons. However, the API does not enforce this; non-MIME-type values can be added as well. All formats are identified by strings that are converted to ASCII lowercase by the API.

dataTransfer . dropEffect [ = value ]

Returns the kind of operation that is currently selected. If the kind of operation isn't one of those that is allowed by the effectAllowed attribute, then the operation will fail.

Can be set, to change the selected operation.

The possible values are none, copy, link, and move.

dataTransfer . effectAllowed [ = value ]

Returns the kinds of operations that are to be allowed.

Can be set, to change the allowed operations.

The possible values are none, copy, copyLink, copyMove, link, linkMove, move, all, and uninitialized,

dataTransfer . types

Returns a DOMStringList listing the formats that were set in the dragstart event. In addition, if any files are being dragged, then one of the types will be the string "Files".

dataTransfer . clearData( [ format ] )

Removes the data of the specified formats. Removes all data if the argument is omitted.

dataTransfer . setData(format, data)

Adds the specified data.

data = dataTransfer . getData(format)

Returns the specified data. If there is no such data, returns the empty string.

dataTransfer . files

Returns a FileList of the files being dragged, if any.

dataTransfer . setDragImage(element, x, y)

Uses the given element to update the drag feedback, replacing any previously specified feedback.

dataTransfer . addElement(element)

Adds the given element to the list of elements used to render the drag feedback.

When a DataTransfer object is created, it must be initialized as follows:

The DataTransfer object must initially contain no data, no elements, and have no associated image.
The DataTransfer object's effectAllowed attribute must be set to "uninitialized".
The dropEffect attribute must be set to "none".

The dropEffect attribute controls the drag-and-drop feedback that the user is given during a drag-and-drop operation.

The attribute must ignore any attempts to set it to a value other than none, copy, link, and move. On getting, the attribute must return the last of those four values that it was set to.

The effectAllowed attribute is used in the drag-and-drop processing model to initialize the dropEffect attribute during the dragenter and dragover events.

The attribute must ignore any attempts to set it to a value other than none, copy, copyLink, copyMove, link, linkMove, move, all, and uninitialized. On getting, the attribute must return the last of those values that it was set to.

The types attribute must return a live DOMStringList that contains the list of formats that were added to the DataTransfer object in the corresponding dragstart event. The same object must be returned each time. If any files were included in the drag, then the DOMStringList object must in addition include the string "Files". (This value can be distinguished from the other values because it is not lowercase.)

The clearData() method, when called with no arguments, must clear the DataTransfer object of all data (for all formats).

The clearData() method does not affect whether any files were included in the drag, so the types attribute's list might still not be empty after calling clearData() (it would still contain the "Files" string if any files were included in the drag).

When called with an argument, the clearData(format) method must clear the DataTransfer object of any data associated with the given format, converted to ASCII lowercase. If format (after conversion to lowercase) is the value "text", then it must be treated as "text/plain". If the format (after conversion to lowercase) is "url", then it must be treated as "text/uri-list".

The setData(format, data) method must add data to the data stored in the DataTransfer object, labeled as being of the type format, converted to ASCII lowercase. This must replace any previous data that had been set for that format. If format (after conversion to lowercase) is the value "text", then it must be treated as "text/plain". If the format (after conversion to lowercase) is "url", then it must be treated as "text/uri-list".

The getData(format) method must return the data that is associated with the type format converted to ASCII lowercase, if any, and must return the empty string otherwise. If format (after conversion to lowercase) is the value "text", then it must be treated as "text/plain". If the format (after conversion to lowercase) is "url", then the data associated with the "text/uri-list" format must be parsed as appropriate for text/uri-list data, and the first URL from the list must be returned. If there is no data with that format, or if there is but it has no URLs, then the method must return the empty string. [RFC2483]

The files attribute must return the FileList object that contains the files that are stored in the DataTransfer object. There is one such object per DataTransfer object.

This version of the API does not expose the types of the files during the drag.

The setDragImage(element, x, y) method sets which element to use to generate the drag feedback. The element argument can be any Element; if it is an img element, then the user agent should use the element's image (at its intrinsic size) to generate the feedback, otherwise the user agent should base the feedback on the given element (but the exact mechanism for doing so is not specified).

The addElement(element) method is an alternative way of specifying how the user agent is to render the drag feedback. It adds an element to the DataTransfer object.

The difference between setDragImage() and addElement() is that the latter automatically generates the image based on the current rendering of the elements added, whereas the former uses the exact specified image.

7.9.3 Events fired during a drag-and-drop action

Status: Last call for comments

The following events are involved in the drag-and-drop model.

Whenever the processing model described below causes one of these events to be fired, the event fired must use the DragEvent interface defined above, must have the bubbling and cancelable behaviors given in the table below, and must have the context information set up as described after the table, with the view attribute set to the view with which the user interacted to trigger the drag-and-drop event, the detail attribute set to zero, the mouse and key attributes set according to the state of the input devices as they would be for user interaction events, and the relatedTarget attribute set to null.

If there is no relevant pointing device, the object must have its screenX, screenY, clientX, clientY, and button attributes set to 0.

Event Name	Target	Bubbles?	Cancelable?	`dataTransfer`	`effectAllowed`	`dropEffect`	Default Action
`dragstart`	Source node	✓ Bubbles	✓ Cancelable	Contains source node unless a selection is being dragged, in which case it is empty; `files` returns any files included in the drag operation	`uninitialized`	`none`	Initiate the drag-and-drop operation
`drag`	Source node	✓ Bubbles	✓ Cancelable	Empty	Same as last event	`none`	Continue the drag-and-drop operation
`dragenter`	Immediate user selection or the body element	✓ Bubbles	✓ Cancelable	Empty	Same as last event	Based on `effectAllowed` value	Reject immediate user selection as potential target element
`dragleave`	Previous target element	✓ Bubbles	—	Empty	Same as last event	`none`	None
`dragover`	Current target element	✓ Bubbles	✓ Cancelable	Empty	Same as last event	Based on `effectAllowed` value	Reset the current drag operation to "none"
`drop`	Current target element	✓ Bubbles	✓ Cancelable	`getData()` returns data set in `dragstart` event; `files` returns any files included in the drag operation	Same as last event	Current drag operation	Varies
`dragend`	Source node	✓ Bubbles	—	Empty	Same as last event	Current drag operation	Varies

"Empty" in the table above means that the getData() and files attributes act as if there is no data being dragged.

The dataTransfer object's contents are empty (the getData() and files attributes act as if there is no data being dragged) except for dragstart events and drop events, for which the contents are set as described in the processing model, below.

The effectAllowed attribute must be set to "uninitialized" for dragstart events, and to whatever value the field had after the last drag-and-drop event was fired for all other events (only counting events fired by the user agent for the purposes of the drag-and-drop model described below).

The dropEffect attribute must be set to "none" for dragstart, drag, and dragleave events (except when stated otherwise in the algorithms given in the sections below), to the value corresponding to the current drag operation for drop and dragend events, and to a value based on the effectAllowed attribute's value and to the drag-and-drop source, as given by the following table, for the remaining events (dragenter and dragover):

`effectAllowed`	`dropEffect`
`none`	`none`
`copy`, `copyLink`, `copyMove`, `all`	`copy`
`link`, `linkMove`	`link`
`move`	`move`
`uninitialized` when what is being dragged is a selection from a text field	`move`
`uninitialized` when what is being dragged is a selection	`copy`
`uninitialized` when what is being dragged is an `a` element with an `href` attribute	`link`
Any other case	`copy`

7.9.4 Drag-and-drop processing model

Status: Last call for comments

When the user attempts to begin a drag operation, the user agent must first determine what is being dragged. If the drag operation was invoked on a selection, then it is the selection that is being dragged. Otherwise, it is the first element, going up the ancestor chain, starting at the node that the user tried to drag, that has the IDL attribute draggable set to true. If there is no such element, then nothing is being dragged, the drag-and-drop operation is never started, and the user agent must not continue with this algorithm.

img elements and a elements with an href attribute have their draggable attribute set to true by default.

If the user agent determines that something can be dragged, a dragstart event must then be fired at the source node.

The source node depends on the kind of drag and how it was initiated. If it is a selection that is being dragged, then the source node is the text node that the user started the drag on (typically the text node that the user originally clicked). If the user did not specify a particular node, for example if the user just told the user agent to begin a drag of "the selection", then the source node is the first text node containing a part of the selection. If it is not a selection that is being dragged, then the source node is the element that is being dragged.

Multiple events are fired on the source node during the course of the drag-and-drop operation.

The list of dragged nodes also depends on the kind of drag. If it is a selection that is being dragged, then the list of dragged nodes contains, in tree order, every node that is partially or completely included in the selection (including all their ancestors). Otherwise, the list of dragged nodes contains only the source node.

If it is a selection that is being dragged, the dataTransfer member of the event must be created with no nodes. Otherwise, it must be created containing just the source node. Script can use the addElement() method to add further elements to the list of what is being dragged. (This list is only used for rendering the drag feedback.)

The dataTransfer member of the event also has data added to it, as follows:

If it is a selection that is being dragged, then the user agent must add the text of the selection to the dataTransfer member, associated with the text/plain format.
If files are being dragged, then the user agent must add the files to the dataTransfer member's files attribute's FileList object. (Dragging files can only happen from outside a browsing context, for example from a file system manager application, and thus the dragstart event is actually implied in this case.)
Perform drag-and-drop initialization steps defined in other relevant specificaations.
The user agent must run the following steps:
1. Let urls be an empty list of absolute URLs.
2. For each node in nodes:
  
  If the node is an a element with an href
  
  Add to urls the result of resolving the element's href content attribute relative to the element.
  
  If the node is an img element with an src
  
  Add to urls the result of resolving the element's src content attribute relative to the element.
3. If urls is still empty, abort these steps.
4. Let url string be the result of concatenating the strings in urls, in the order they were added, separated by a U+000D CARRIAGE RETURN U+000A LINE FEED character pair (CRLF).
5. Add url string to the dataTransfer member, associated with the text/uri-list format.

If the event is canceled, then the drag-and-drop operation must not occur; the user agent must not continue with this algorithm.

If it is not canceled, then the drag-and-drop operation must be initiated.

Since events with no event listeners registered are, almost by definition, never canceled, drag-and-drop is always available to the user if the author does not specifically prevent it.

The drag-and-drop feedback must be generated from the first of the following sources that is available:

The element specified in the last call to the setDragImage() method of the dataTransfer object of the dragstart event, if the method was called. In visual media, if this is used, the x and y arguments that were passed to that method should be used as hints for where to put the cursor relative to the resulting image. The values are expressed as distances in CSS pixels from the left side and from the top side of the image respectively. [CSS]
The elements that were added to the dataTransfer object, both before the event was fired, and during the handling of the event using the addElement() method, if any such elements were indeed added.
The selection that the user is dragging.

The user agent must take a note of the data that was placed in the dataTransfer object. This data will be made available again when the drop event is fired.

From this point until the end of the drag-and-drop operation, device input events (e.g. mouse and keyboard events) must be suppressed. In addition, the user agent must track all DOM changes made during the drag-and-drop operation, and add them to its undo history as one atomic operation once the drag-and-drop operation has ended.

During the drag operation, the element directly indicated by the user as the drop target is called the immediate user selection. (Only elements can be selected by the user; other nodes must not be made available as drop targets.) However, the immediate user selection is not necessarily the current target element, which is the element currently selected for the drop part of the drag-and-drop operation. The immediate user selection changes as the user selects different elements (either by pointing at them with a pointing device, or by selecting them in some other way). The current target element changes when the immediate user selection changes, based on the results of event listeners in the document, as described below.

Both the current target element and the immediate user selection can be null, which means no target element is selected. They can also both be elements in other (DOM-based) documents, or other (non-Web) programs altogether. (For example, a user could drag text to a word-processor.) The current target element is initially null.

In addition, there is also a current drag operation, which can take on the values "none", "copy", "link", and "move". Initially, it has the value "none". It is updated by the user agent as described in the steps below.

User agents must, as soon as the drag operation is initiated and every 350ms (±200ms) thereafter for as long as the drag operation is ongoing, queue a task to perform the following steps in sequence:

If the user agent is still performing the previous iteration of the sequence (if any) when the next iteration becomes due, the user agent must not execute the overdue iteration, effectively "skipping missed frames" of the drag-and-drop operation.
The user agent must fire a drag event at the source node. If this event is canceled, the user agent must set the current drag operation to none (no drag operation).

Next, if the drag event was not canceled and the user has not ended the drag-and-drop operation, the user agent must check the state of the drag-and-drop operation, as follows:

First, if the user is indicating a different immediate user selection than during the last iteration (or if this is the first iteration), and if this immediate user selection is not the same as the current target element, then the current target element must be updated, as follows:

If the new immediate user selection is null, or is in a non-DOM document or application

The user agent must set the current target element to the same value.

Otherwise

The user agent must fire a dragenter event at the immediate user selection.

If the event is canceled, then the current target element must be set to the immediate user selection.

Otherwise, the user agent must act as follows:

If the current target element is a text field (e.g. textarea, or an input element whose type attribute is in the Text state) or an editable element

The current target element must be set to the immediate user selection anyway.

If the current target element is the body element

The current target element is left unchanged.

Otherwise

The user agent must fire a dragenter event at the body element, and the current target element must be set to the body element, regardless of whether that event was canceled or not. (If the body element is null, then the current target element would be set to null too in this case, it wouldn't be set to the Document object.)
If the previous step caused the current target element to change, and if the previous target element was not null or a part of a non-DOM document, the user agent must fire a dragleave event at the previous target element.

If the current target element is a DOM element, the user agent must fire a dragover event at this current target element.

If the dragover event is not canceled, the user agent must act as follows:

If the current target element is a text field (e.g. textarea, or an input element whose type attribute is in the Text state) or an editable element: The user agent must set the current drag operation to either "copy" or "move", as appropriate given the platform conventions.
Otherwise: The user agent must reset the current drag operation to "none".

Otherwise (if the dragover event is canceled), the current drag operation must be set based on the values the effectAllowed and dropEffect attributes of the dataTransfer object had after the event was handled, as per the following table:

`effectAllowed`	`dropEffect`	Drag operation
`uninitialized`, `copy`, `copyLink`, `copyMove`, or `all`	`copy`	"copy"
`uninitialized`, `link`, `copyLink`, `linkMove`, or `all`	`link`	"link"
`uninitialized`, `move`, `copyMove`, `linkMove`, or `all`	`move`	"move"
Any other case		"none"

Then, regardless of whether the dragover event was canceled or not, the drag feedback (e.g. the mouse cursor) must be updated to match the current drag operation, as follows:

Drag operation	Feedback
"copy"	Data will be copied if dropped here.
"link"	Data will be linked if dropped here.
"move"	Data will be moved if dropped here.
"none"	No operation allowed, dropping here will cancel the drag-and-drop operation.

Otherwise, if the current target element is not a DOM element, the user agent must use platform-specific mechanisms to determine what drag operation is being performed (none, copy, link, or move). This sets the current drag operation.

Otherwise, if the user ended the drag-and-drop operation (e.g. by releasing the mouse button in a mouse-driven drag-and-drop interface), or if the drag event was canceled, then this will be the last iteration. The user agent must execute the following steps, then stop looping.
1. If the current drag operation is none (no drag operation), or, if the user ended the drag-and-drop operation by canceling it (e.g. by hitting the Escape key), or if the current target element is null, then the drag operation failed. If the current target element is a DOM element, the user agent must fire a dragleave event at it; otherwise, if it is not null, it must use platform-specific conventions for drag cancellation.
2. Otherwise, the drag operation was as success. If the current target element is a DOM element, the user agent must fire a drop event at it; otherwise, it must use platform-specific conventions for indicating a drop.
  
  When the target is a DOM element, the dropEffect attribute of the event's dataTransfer object must be given the value representing the current drag operation (copy, link, or move), and the object must be set up so that the getData() method will return the data that was added during the dragstart event, and the files attribute will return a FileList object with any files that were dragged.
  
  If the event is canceled, the current drag operation must be set to the value of the dropEffect attribute of the event's dataTransfer object as it stood after the event was handled.
  
  Otherwise, the event is not canceled, and the user agent must perform the event's default action, which depends on the exact target as follows:
  
  If the current target element is a text field (e.g. textarea, or an input element whose type attribute is in the Text state) or an editable element
  
  The user agent must insert the data associated with the text/plain format, if any, into the text field or editable element in a manner consistent with platform-specific conventions (e.g. inserting it at the current mouse cursor position, or inserting it at the end of the field).
  
  Otherwise
  
  Reset the current drag operation to "none".
3. Finally, the user agent must fire a dragend event at the source node, with the dropEffect attribute of the event's dataTransfer object being set to the value corresponding to the current drag operation.
  
  The current drag operation can change during the processing of the drop event, if one was fired.
  
  The event is not cancelable. After the event has been handled, the user agent must act as follows:
  
  If the current target element is a text field (e.g. textarea, or an input element whose type attribute is in the Text state), and a drop event was fired in the previous step, and the current drag operation is "move", and the source of the drag-and-drop operation is a selection in the DOM
  
  The user agent should delete the range representing the dragged selection from the DOM.
  
  If the current target element is a text field (e.g. textarea, or an input element whose type attribute is in the Text state), and a drop event was fired in the previous step, and the current drag operation is "move", and the source of the drag-and-drop operation is a selection in a text field
  
  The user agent should delete the dragged selection from the relevant text field.
  
  Otherwise
  
  The event has no default action.

7.9.4.1 When the drag-and-drop operation starts or ends in another document

Status: Last call for comments

The model described above is independent of which Document object the nodes involved are from; the events must be fired as described above and the rest of the processing model must be followed as described above, irrespective of how many documents are involved in the operation.

7.9.4.2 When the drag-and-drop operation starts or ends in another application

Status: Last call for comments

If the drag is initiated in another application, the source node is not a DOM node, and the user agent must use platform-specific conventions instead when the requirements above involve the source node. User agents in this situation must act as if the dragged data had been added to the DataTransfer object when the drag started, even though no dragstart event was actually fired; user agents must similarly use platform-specific conventions when deciding on what drag feedback to use.

All the format strings must be converted to ASCII lowercase. If the platform conventions do not use MIME types to label the dragged data, the user agent must map the types to MIME types first.

If a drag is started in a document but ends in another application, then the user agent must instead replace the parts of the processing model relating to handling the target according to platform-specific conventions.

In any case, scripts running in the context of the document must not be able to distinguish the case of a drag-and-drop operation being started or ended in another application from the case of a drag-and-drop operation being started or ended in another document from another domain.

7.9.5 The `draggable` attribute

Status: Last call for comments

All HTML elements may have the draggable content attribute set. The draggable attribute is an enumerated attribute. It has three states. The first state is true and it has the keyword true. The second state is false and it has the keyword false. The third state is auto; it has no keywords but it is the missing value default.

The true state means the element is draggable; the false state means that it is not. The auto state uses the default behavior of the user agent.

element . draggable [ = value ]

Returns true if the element is draggable; otherwise, returns false.

Can be set, to override the default and set the draggable content attribute.

The draggable IDL attribute, whose value depends on the content attribute's in the way described below, controls whether or not the element is draggable. Generally, only text selections are draggable, but elements whose draggable IDL attribute is true become draggable as well.

If an element's draggable content attribute has the state true, the draggable IDL attribute must return true.

Otherwise, if the element's draggable content attribute has the state false, the draggable IDL attribute must return false.

Otherwise, the element's draggable content attribute has the state auto. If the element is an img element, or, if the element is an a element with an href content attribute, the draggable IDL attribute must return true.

Otherwise, the draggable DOM must return false.

If the draggable IDL attribute is set to the value false, the draggable content attribute must be set to the literal value false. If the draggable IDL attribute is set to the value true, the draggable content attribute must be set to the literal value true.

7.9.6 Security risks in the drag-and-drop model

Status: Last call for comments

User agents must not make the data added to the DataTransfer object during the dragstart event available to scripts until the drop event, because otherwise, if a user were to drag sensitive information from one document to a second document, crossing a hostile third document in the process, the hostile document could intercept the data.

For the same reason, user agents must consider a drop to be successful only if the user specifically ended the drag operation — if any scripts end the drag operation, it must be considered unsuccessful (canceled) and the drop event must not be fired.

User agents should take care to not start drag-and-drop operations in response to script actions. For example, in a mouse-and-window environment, if a script moves a window while the user has his mouse button depressed, the UA would not consider that to start a drag. This is important because otherwise UAs could cause data to be dragged from sensitive sources and dropped into hostile documents without the user's consent.

7.10 Undo history

Status: Last call for comments

7.10.1 Definitions

Status: Last call for comments

The user agent must associate an undo transaction history with each HTMLDocument object.

The undo transaction history is a list of entries. The entries are of two types: DOM changes and undo objects.

Each DOM changes entry in the undo transaction history consists of batches of one or more of the following:

Changes to the content attributes of an Element node.
Changes to the DOM hierarchy of nodes that are descendants of the HTMLDocument object (parentNode, childNodes).
Changes to internal state, such as a form control's value or dirty checkedness flag.

Undo object entries consist of objects representing state that scripts running in the document are managing. For example, a Web mail application could use an undo object to keep track of the fact that a user has moved an e-mail to a particular folder, so that the user can undo the action and have the e-mail return to its former location.

Broadly speaking, DOM changes entries are handled by the UA in response to user edits of form controls and editing hosts on the page, and undo object entries are handled by script in response to higher-level user actions (such as interactions with server-side state, or in the implementation of a drawing tool).

7.10.2 The `UndoManager` interface

Status: Last call for comments

To manage undo object entries in the undo transaction history, the UndoManager interface can be used:

interface UndoManager {
  readonly attribute unsigned long length;
  getter any item(in unsigned long index);
  readonly attribute unsigned long position;
  unsigned long add(in any data, in DOMString title);
  void remove(in unsigned long index);
  void clearUndo();
  void clearRedo();
};

window . undoManager

Returns the UndoManager object.

undoManager . length

Returns the number of entries in the undo history.

data = undoManager . item(index)

undoManager[index]

Returns the entry with index index in the undo history.

Returns null if index is out of range.

undoManager . position

Returns the number of the current entry in the undo history. (Entries at and past this point are redo entries.)

undoManager . add(data, title)

Adds the specified entry to the undo history.

undoManager . remove(index)

Removes the specified entry to the undo history.

Throws an INDEX_SIZE_ERR exception if the given index is out of range.

undoManager . clearUndo()

Removes all entries before the current position in the undo history.

undoManager . clearRedo()

Removes all entries at and after the current position in the undo history.

The undoManager attribute of the Window interface must return the object implementing the UndoManager interface for that Window object's associated HTMLDocument object.

UndoManager objects represent their document's undo transaction history. Only undo object entries are visible with this API, but this does not mean that DOM changes entries are absent from the undo transaction history.

The length attribute must return the number of undo object entries in the undo transaction history. This is the length.

The object's indices of the supported indexed properties are the numbers in the range zero to length-1, unless the length is zero, in which case there are no supported indexed properties.

The item(n) method must return the nth undo object entry in the undo transaction history, if there is one, or null otherwise.

The undo transaction history has a current position. This is the position between two entries in the undo transaction history's list where the previous entry represents what needs to happen if the user invokes the "undo" command (the "undo" side, lower numbers), and the next entry represents what needs to happen if the user invokes the "redo" command (the "redo" side, higher numbers).

The position attribute must return the index of the undo object entry nearest to the undo position, on the "redo" side. If there are no undo object entries on the "redo" side, then the attribute must return the same as the length attribute. If there are no undo object entries on the "undo" side of the undo position, the position attribute returns zero.

Since the undo transaction history contains both undo object entries and DOM changes entries, but the position attribute only returns indices relative to undo object entries, it is possible for several "undo" or "redo" actions to be performed without the value of the position attribute changing.

The add(data, title) method's behavior depends on the current state. Normally, it must insert the data object passed as an argument into the undo transaction history immediately before the undo position, optionally remembering the given title to use in the UI. If the method is called during an undo operation, however, the object must instead be added immediately after the undo position.

If the method is called and there is neither an undo operation in progress nor a redo operation in progress then any entries in the undo transaction history after the undo position must be removed (as if clearRedo() had been called).

The remove(index) method must remove the undo object entry with the specified index. If the index is less than zero or greater than or equal to length then the method must raise an INDEX_SIZE_ERR exception. DOM changes entries are unaffected by this method.

The clearUndo() method must remove all entries in the undo transaction history before the undo position, be they DOM changes entries or undo object entries.

The clearRedo() method must remove all entries in the undo transaction history after the undo position, be they DOM changes entries or undo object entries.

7.10.3 Undo: moving back in the undo transaction history

Status: Last call for comments

When the user invokes an undo operation, or when the execCommand() method is called with the undo command, the user agent must perform an undo operation.

If the undo position is at the start of the undo transaction history, then the user agent must do nothing.

If the entry immediately before the undo position is a DOM changes entry, then the user agent must remove that DOM changes entry, reverse the DOM changes that were listed in that entry, and, if the changes were reversed with no problems, add a new DOM changes entry (consisting of the opposite of those DOM changes) to the undo transaction history on the other side of the undo position.

If the DOM changes cannot be undone (e.g. because the DOM state is no longer consistent with the changes represented in the entry), then the user agent must simply remove the DOM changes entry, without doing anything else.

If the entry immediately before the undo position is an undo object entry, then the user agent must first remove that undo object entry from the undo transaction history, and then must fire an undo event at the Window object, using the undo object entry's associated undo object as the event's data.

Any calls to add() while the event is being handled will be used to populate the redo history, and will then be used if the user invokes the "redo" command to undo his undo.

7.10.4 Redo: moving forward in the undo transaction history

Status: Last call for comments

When the user invokes a redo operation, or when the execCommand() method is called with the redo command, the user agent must perform a redo operation.

This is mostly the opposite of an undo operation, but the full definition is included here for completeness.

If the undo position is at the end of the undo transaction history, then the user agent must do nothing.

If the entry immediately after the undo position is a DOM changes entry, then the user agent must remove that DOM changes entry, reverse the DOM changes that were listed in that entry, and, if the changes were reversed with no problems, add a new DOM changes entry (consisting of the opposite of those DOM changes) to the undo transaction history on the other side of the undo position.

If the DOM changes cannot be redone (e.g. because the DOM state is no longer consistent with the changes represented in the entry), then the user agent must simply remove the DOM changes entry, without doing anything else.

If the entry immediately after the undo position is an undo object entry, then the user agent must first remove that undo object entry from the undo transaction history, and then must fire a redo event at the Window object, using the undo object entry's associated undo object as the event's data.

7.10.5 The `UndoManagerEvent` interface and the `undo` and `redo` events

Status: Last call for comments

interface UndoManagerEvent : Event {
  readonly attribute any data;
  void initUndoManagerEvent(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in any dataArg);
};

event . data: Returns the data that was passed to the add() method.

The initUndoManagerEvent() method must initialize the event in a manner analogous to the similarly-named method in the DOM Events interfaces. [DOMEVENTS]

The data attribute represents the undo object for the event.

The undo and redo events do not bubble, cannot be canceled, and have no default action. When the user agent fires one of these events it must use the UndoManagerEvent interface, with the data field containing the relevant undo object.

7.10.6 Implementation notes

Status: Last call for comments

How user agents present the above conceptual model to the user is not defined. The undo interface could be a filtered view of the undo transaction history, it could manipulate the undo transaction history in ways not described above, and so forth. For example, it is possible to design a UA that appears to have separate undo transaction histories for each form control; similarly, it is possible to design systems where the user has access to more undo information than is present in the official (as described above) undo transaction history (such as providing a tree-based approach to document state). Such UI models should be based upon the single undo transaction history described in this section, however, such that to a script there is no detectable difference.

7.11 Editing APIs

Status: Last call for comments

document . execCommand(commandId [, showUI [, value ] ] ): Runs the action specified by the first argument, as described in the list below. The second and third arguments sometimes affect the action. (If they don't they are ignored.)
document . queryCommandEnabled(commandId): Returns whether the given command is enabled, as described in the list below.
document . queryCommandIndeterm(commandId): Returns whether the given command is indeterminate, as described in the list below.
document . queryCommandState(commandId): Returns the state of the command, as described in the list below.
document . queryCommandSupported(commandId): Returns true if the command is supported; otherwise, returns false.
document . queryCommandValue(commandId): Returns the value of the command, as described in the list below.

The execCommand(commandId, showUI, value) method on the HTMLDocument interface allows scripts to perform actions on the current selection or at the current caret position. Generally, these commands would be used to implement editor UI, for example having a "delete" button on a toolbar.

There are three variants to this method, with one, two, and three arguments respectively. The showUI and value parameters, even if specified, are ignored except where otherwise stated.

When execCommand() is invoked, the user agent must follow the following steps:

If the given commandId maps to an entry in the list below whose "Enabled When" entry has a condition that is currently false, do nothing; abort these steps.
Otherwise, execute the "Action" listed below for the given commandId.

A document is ready for editing host commands if it has a selection that is entirely within an editing host, or if it has no selection but its caret is inside an editing host.

The queryCommandEnabled(commandId) method, when invoked, must return true if the condition listed below under "Enabled When" for the given commandId is true, and false otherwise.

The queryCommandIndeterm(commandId) method, when invoked, must return true if the condition listed below under "Indeterminate When" for the given commandId is true, and false otherwise.

The queryCommandState(commandId) method, when invoked, must return the value expressed below under "State" for the given commandId.

The queryCommandSupported(commandId) method, when invoked, must return true if the given commandId is in the list below, and false otherwise.

The queryCommandValue(commandId) method, when invoked, must return the value expressed below under "Value" for the given commandId.

The possible values for commandId, and their corresponding meanings, are as follows. These values must be compared to the argument in an ASCII case-insensitive manner.

bold

Summary: Toggles whether the selection is bold.

Action: The user agent must act as if the user had requested that the selection be wrapped in the semantics of the b element (or, again, unwrapped, or have that semantic inserted or removed, as defined by the UA).

Enabled When: The document is ready for editing host commands.

Indeterminate When: Never.

State: True if the selection, or the caret, if there is no selection, is, or is contained within, a b element. False otherwise.

Value: The string "true" if the expression given for the "State" above is true, the string "false" otherwise.

createLink

Summary: Toggles whether the selection is a link or not. If the second argument is true, and a link is to be added, the user agent will ask the user for the address. Otherwise, the third argument will be used as the address.

Action: The user agent must act as if the user had requested that the selection be wrapped in the semantics of the a element (or, again, unwrapped, or have that semantic inserted or removed, as defined by the UA). If the user agent creates an a element or modifies an existing a element, then if the showUI argument is present and has the value false, then the value of the value argument must be used as the URL of the link. Otherwise, the user agent should prompt the user for the URL of the link.

Enabled When: The document is ready for editing host commands.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

delete

Summary: Deletes the selection or the character before the cursor.

Action: The user agent must act as if the user had performed a backspace operation.

Enabled When: The document is ready for editing host commands.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

formatBlock

Summary: Wraps the selection in the element given by the second argument. If the second argument doesn't specify an element that is a formatBlock candidate, does nothing.

Action: The user agent must run the following steps:

If the value argument wasn't specified, abort these steps without doing anything.
If the value argument has a leading U+003C LESS-THAN SIGN character (<) and a trailing U+003E GREATER-THAN SIGN character (>), then remove the first and last characters from value.
If value is (now) an ASCII case-insensitive match for the tag name of an element defined by this specification that is defined to be a formatBlock candidate, then, for every position in the selection, take the nearest formatBlock candidate ancestor element of that position that contains only phrasing content, and, if that element is editable, is not an editing host, and has a parent element whose content model allows that parent to contain any flow content, replace it with an element in the HTML namespace whose name is value, and move all the children that were in it to the new element, and copy all the attributes that were on it to the new element.

If there is no selection, then, where in the description above refers to the selection, the user agent must act as if the selection was an empty range (with just one position) at the caret position.

Enabled When: The document is ready for editing host commands.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

forwardDelete

Summary: Deletes the selection or the character after the cursor.

Action: The user agent must act as if the user had performed a forward delete operation.

Enabled When: The document is ready for editing host commands.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

insertImage

Summary: Toggles whether the selection is an image or not. If the second argument is true, and an image is to be added, the user agent will ask the user for the address. Otherwise, the third argument will be used as the address.

Action: The user agent must act as if the user had requested that the selection be wrapped in the semantics of the img element (or, again, unwrapped, or have that semantic inserted or removed, as defined by the UA). If the user agent creates an img element or modifies an existing img element, then if the showUI argument is present and has the value false, then the value of the value argument must be used as the URL of the image. Otherwise, the user agent should prompt the user for the URL of the image.

Enabled When: The document is ready for editing host commands.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

insertHTML

Summary: Replaces the selection with the value of the third argument parsed as HTML.

Action: The user agent must run the following steps:

If the document is an XML document, then throw an INVALID_ACCESS_ERR exception and abort these steps.
If the value argument wasn't specified, abort these steps without doing anything.
If there is a selection, act as if the user had requested that the selection be deleted.
Invoke the HTML fragment parsing algorithm with an arbitrary orphan body element owned by the same Document as the context element and with the value argument as input.
Insert the nodes returned by the previous step into the document at the location of the caret, firing any mutation events as appropriate.

Enabled When: The document is ready for editing host commands.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

insertLineBreak

Summary: Inserts a line break.

Action: The user agent must act as if the user had requested a line separator.

Enabled When: The document is ready for editing host commands.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

insertOrderedList

Summary: Toggles whether the selection is an ordered list.

Action: The user agent must act as if the user had requested that the selection be wrapped in the semantics of the ol element (or unwrapped, or, if there is no selection, have that semantic inserted or removed — the exact behavior is UA-defined).

Enabled When: The document is ready for editing host commands.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

insertUnorderedList

Summary: Toggles whether the selection is an unordered list.

Action: The user agent must act as if the user had requested that the selection be wrapped in the semantics of the ul element (or unwrapped, or, if there is no selection, have that semantic inserted or removed — the exact behavior is UA-defined).

Enabled When: The document is ready for editing host commands.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

insertParagraph

Summary: Inserts a paragraph break.

Action: The user agent must act as if the user had performed a break block editing action.

Enabled When: The document is ready for editing host commands.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

insertText

Summary: Inserts the text given in the third parameter.

Action: The user agent must act as if the user had inserted text corresponding to the value parameter.

Enabled When: The document is ready for editing host commands.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

italic

Summary: Toggles whether the selection is italic.

Action: The user agent must act as if the user had requested that the selection be wrapped in the semantics of the i element (or, again, unwrapped, or have that semantic inserted or removed, as defined by the UA).

Enabled When: The document is ready for editing host commands.

Indeterminate When: Never.

State: True if the selection, or the caret, if there is no selection, is, or is contained within, a i element. False otherwise.

Value: The string "true" if the expression given for the "State" above is true, the string "false" otherwise.

redo

Summary: Acts as if the user had requested a redo.

Action: The user agent must move forward one step in its undo transaction history, restoring the associated state. If the undo position is at the end of the undo transaction history, the user agent must do nothing. See the undo history.

Enabled When: The undo position is not at the end of the undo transaction history.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

selectAll

Summary: Selects all the editable content.

Action: The user agent must change the selection so that all the content in the currently focused editing host is selected. If no editing host is focused, then the content of the entire document must be selected.

Enabled When: Always.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

subscript

Summary: Toggles whether the selection is subscripted.

Action: The user agent must act as if the user had requested that the selection be wrapped in the semantics of the sub element (or, again, unwrapped, or have that semantic inserted or removed, as defined by the UA).

Enabled When: The document is ready for editing host commands.

Indeterminate When: Never.

State: True if the selection, or the caret, if there is no selection, is, or is contained within, a sub element. False otherwise.

Value: The string "true" if the expression given for the "State" above is true, the string "false" otherwise.

superscript

Summary: Toggles whether the selection is superscripted.

Action: The user agent must act as if the user had requested that the selection be wrapped in the semantics of the sup element (or unwrapped, or, if there is no selection, have that semantic inserted or removed — the exact behavior is UA-defined).

Enabled When: The document is ready for editing host commands.

Indeterminate When: Never.

State: True if the selection, or the caret, if there is no selection, is, or is contained within, a sup element. False otherwise.

Value: The string "true" if the expression given for the "State" above is true, the string "false" otherwise.

undo

Summary: Acts as if the user had requested an undo.

Action: The user agent must move back one step in its undo transaction history, restoring the associated state. If the undo position is at the start of the undo transaction history, the user agent must do nothing. See the undo history.

Enabled When: The undo position is not at the start of the undo transaction history.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

unlink

Summary: Removes all links from the selection.

Action: The user agent must remove all a elements that have href attributes and that are partially or completely included in the current selection.

Enabled When: The document has a selection that is entirely within an editing host and that contains (either partially or completely) at least one a element that has an href attribute.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

unselect

Summary: Unselects everything.

Action: The user agent must change the selection so that nothing is selected.

Enabled When: Always.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

vendorID-customCommandID

Action: User agents may implement vendor-specific extensions to this API. Vendor-specific extensions to the list of commands should use the syntax vendorID-customCommandID so as to prevent clashes between extensions from different vendors and future additions to this specification.

Enabled When: UA-defined.

Indeterminate When: UA-defined.

State: UA-defined.

Value: UA-defined.

Anything else

Action: User agents must do nothing.

Enabled When: Never.

Indeterminate When: Never.

State: Always false.

Value: Always the string "false".

8 The HTML syntax

This section only describes the rules for resources labeled with an HTML MIME type. Rules for XML resources are discussed in the section below entitled "The XHTML syntax".

8.1 Writing HTML documents

Status: Last call for comments

This section only applies to documents, authoring tools, and markup generators. In particular, it does not apply to conformance checkers; conformance checkers must use the requirements given in the next section ("parsing HTML documents").

Documents must consist of the following parts, in the given order:

Optionally, a single U+FEFF BYTE ORDER MARK (BOM) character.
Any number of comments and space characters.
A DOCTYPE.
Any number of comments and space characters.
The root element, in the form of an html element.
Any number of comments and space characters.

The various types of content mentioned above are described in the next few sections.

In addition, there are some restrictions on how character encoding declarations are to be serialized, as discussed in the section on that topic.

Space characters before the root html element, and space characters at the start of the html element and before the head element, will be dropped when the document is parsed; space characters after the root html element will be parsed as if they were at the end of the body element. Thus, space characters around the root element do not round-trip.

It is suggested that newlines be inserted after the DOCTYPE, after any comments that are before the root element, after the html element's start tag (if it is not omitted), and after any comments that are inside the html element but before the head element.

Many strings in the HTML syntax (e.g. the names of elements and their attributes) are case-insensitive, but only for characters in the ranges U+0041 to U+005A (LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z) and U+0061 to U+007A (LATIN SMALL LETTER A to LATIN SMALL LETTER Z). For convenience, in this section this is just referred to as "case-insensitive".

8.1.1 The DOCTYPE

Status: Last call for comments. ISSUE-4 (html-versioning) and ISSUE-84 (legacy-doctypes) block progress to Last Call

A DOCTYPE is a mostly useless, but required, header.

DOCTYPEs are required for legacy reasons. When omitted, browsers tend to use a different rendering mode that is incompatible with some specifications. Including the DOCTYPE in a document ensures that the browser makes a best-effort attempt at following the relevant specifications.

A DOCTYPE must consist of the following characters, in this order:

A U+003C LESS-THAN SIGN character (<).
A U+0021 EXCLAMATION MARK character (!).
A string that is an ASCII case-insensitive match for the string "DOCTYPE".
One or more space characters.
A string that is an ASCII case-insensitive match for the string "HTML".
Optionally, a DOCTYPE legacy string or an obsolete permitted DOCTYPE string (defined below).
Zero or more space characters.
A U+003E GREATER-THAN SIGN character (>).

In other words, <!DOCTYPE HTML>, case-insensitively.

For the purposes of HTML generators that cannot output HTML markup with the short DOCTYPE "<!DOCTYPE HTML>", a DOCTYPE legacy string may be inserted into the DOCTYPE (in the position defined above). This string must consist of:

One or more space characters.
A string that is an ASCII case-insensitive match for the string "SYSTEM".
One or more space characters.
A U+0022 QUOTATION MARK or U+0027 APOSTROPHE character (the quote mark).
The literal string "about:legacy-compat".
A matching U+0022 QUOTATION MARK or U+0027 APOSTROPHE character (i.e. the same character as in the earlier step labeled quote mark).

In other words, <!DOCTYPE HTML SYSTEM "about:legacy-compat"> or <!DOCTYPE HTML SYSTEM 'about:legacy-compat'>, case-insensitively except for the bit in single or double quotes.

The DOCTYPE legacy string should not be used unless the document is generated from a system that cannot output the shorter string.

To help authors transition from HTML4 and XHTML1, an obsolete permitted DOCTYPE string can be inserted into the DOCTYPE (in the position defined above). This string must consist of:

One or more space characters.
A string that is an ASCII case-insensitive match for the string "PUBLIC".
One or more space characters.
A U+0022 QUOTATION MARK or U+0027 APOSTROPHE character (the first quote mark).
The string from one of the cells in the first column of the table below. The row to which this cell belongs is the selected row.
A matching U+0022 QUOTATION MARK or U+0027 APOSTROPHE character (i.e. the same character as in the earlier step labeled first quote mark).
If the cell in the second column of the selected row is not blank, one or more space characters.
If the cell in the second column of the selected row is not blank, a U+0022 QUOTATION MARK or U+0027 APOSTROPHE character (the third quote mark).
If the cell in the second column of the selected row is not blank, the string from the cell in the second column of the selected row.
If the cell in the second column of the selected row is not blank, a matching U+0022 QUOTATION MARK or U+0027 APOSTROPHE character (i.e. the same character as in the earlier step labeled third quote mark).

Allowed values for public and system identifiers in an obsolete permitted DOCTYPE string.
Public identifier	System identifier
`-//W3C//DTD HTML 4.0//EN`
`-//W3C//DTD HTML 4.0//EN`	`http://www.w3.org/TR/REC-html40/strict.dtd`
`-//W3C//DTD HTML 4.01//EN`
`-//W3C//DTD HTML 4.01//EN`	`http://www.w3.org/TR/html4/strict.dtd`
`-//W3C//DTD XHTML 1.0 Strict//EN`	`http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd`
`-//W3C//DTD XHTML 1.1//EN`	`http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd`

A DOCTYPE containing an obsolete permitted DOCTYPE string is an obsolete permitted DOCTYPE. Authors should not use obsolete permitted DOCTYPEs, as they are unnecessarily long.

8.1.2 Elements

Status: Last call for comments

There are five different kinds of elements: void elements, raw text elements, RCDATA elements, foreign elements, and normal elements.

Void elements: area, base, br, col, command, embed, hr, img, input, keygen, link, meta, param, source
Raw text elements: script, style
RCDATA elements: textarea, title
Foreign elements: Elements from the MathML namespace and the SVG namespace.
Normal elements: All other allowed HTML elements are normal elements.

Tags are used to delimit the start and end of elements in the markup. Raw text, RCDATA, and normal elements have a start tag to indicate where they begin, and an end tag to indicate where they end. The start and end tags of certain normal elements can be omitted, as described later. Those that cannot be omitted must not be omitted. Void elements only have a start tag; end tags must not be specified for void elements. Foreign elements must either have a start tag and an end tag, or a start tag that is marked as self-closing, in which case they must not have an end tag.

The contents of the element must be placed between just after the start tag (which might be implied, in certain cases) and just before the end tag (which again, might be implied in certain cases). The exact allowed contents of each individual element depends on the content model of that element, as described earlier in this specification. Elements must not contain content that their content model disallows. In addition to the restrictions placed on the contents by those content models, however, the five types of elements have additional syntactic requirements.

Void elements can't have any contents (since there's no end tag, no content can be put between the start tag and the end tag).

Raw text elements can have text, though it has restrictions described below.

RCDATA elements can have text and character references, but the text must not contain an ambiguous ampersand. There are also further restrictions described below.

Foreign elements whose start tag is marked as self-closing can't have any contents (since, again, as there's no end tag, no content can be put between the start tag and the end tag). Foreign elements whose start tag is not marked as self-closing can have text, character references, CDATA sections, other elements, and comments, but the text must not contain the character U+003C LESS-THAN SIGN (<) or an ambiguous ampersand.

The HTML syntax does not support namespace declarations, even in foreign elements.

For instance, consider the following HTML fragment:

<p>
 <svg>
  <metadata>
   <!-- this is invalid -->
   <cdr:license xmlns:cdr="http://www.example.com/cdr/metadata" name="MIT"/>
  </metadata>
 </svg>
</p>

The innermost element, cdr:license, is actually in the SVG namespace, as the "xmlns:cdr" attribute has no effect (unlike in XML). In fact, as the comment in the fragment above says, the fragment is actually non-conforming. This is because the SVG specification does not define any elements called "cdr:license" in the SVG namespace.

Normal elements can have text, character references, other elements, and comments, but the text must not contain the character U+003C LESS-THAN SIGN (<) or an ambiguous ampersand. Some normal elements also have yet more restrictions on what content they are allowed to hold, beyond the restrictions imposed by the content model and those described in this paragraph. Those restrictions are described below.

Tags contain a tag name, giving the element's name. HTML elements all have names that only use characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), U+0061 LATIN SMALL LETTER A to U+007A LATIN SMALL LETTER Z, and U+0041 LATIN CAPITAL LETTER A to U+005A LATIN CAPITAL LETTER Z. In the HTML syntax, tag names, even those for foreign elements, may be written with any mix of lower- and uppercase letters that, when converted to all-lowercase, matches the element's tag name; tag names are case-insensitive.

8.1.2.1 Start tags

Status: Last call for comments

Start tags must have the following format:

The first character of a start tag must be a U+003C LESS-THAN SIGN character (<).
The next few characters of a start tag must be the element's tag name.
If there are to be any attributes in the next step, there must first be one or more space characters.
Then, the start tag may have a number of attributes, the syntax for which is described below. Attributes may be separated from each other by one or more space characters.
After the attributes, or after the tag name if there are no attributes, there may be one or more space characters. (Some attributes are required to be followed by a space. See the attributes section below.)
Then, if the element is one of the void elements, or if the element is a foreign element, then there may be a single U+002F SOLIDUS character (/). This character has no effect on void elements, but on foreign elements it marks the start tag as self-closing.
Finally, start tags must be closed by a U+003E GREATER-THAN SIGN character (>).

8.1.2.2 End tags

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End tags must have the following format:

The first character of an end tag must be a U+003C LESS-THAN SIGN character (<).
The second character of an end tag must be a U+002F SOLIDUS character (/).
The next few characters of an end tag must be the element's tag name.
After the tag name, there may be one or more space characters.
Finally, end tags must be closed by a U+003E GREATER-THAN SIGN character (>).

8.1.2.3 Attributes

Status: Last call for comments

Attributes for an element are expressed inside the element's start tag.

Attributes have a name and a value. Attribute names must consist of one or more characters other than the space characters, U+0000 NULL, U+0022 QUOTATION MARK ("), U+0027 APOSTROPHE ('), U+003E GREATER-THAN SIGN (>), U+002F SOLIDUS (/), and U+003D EQUALS SIGN (=) characters, the control characters, and any characters that are not defined by Unicode. In the HTML syntax, attribute names, even those for foreign elements, may be written with any mix of lower- and uppercase letters that are an ASCII case-insensitive match for the attribute's name.

Attribute values are a mixture of text and character references, except with the additional restriction that the text cannot contain an ambiguous ampersand.

Attributes can be specified in four different ways:

Empty attribute syntax

Just the attribute name. The value is implicitly the empty string.

In the following example, the disabled attribute is given with the empty attribute syntax:

<input disabled>

If an attribute using the empty attribute syntax is to be followed by another attribute, then there must be a space character separating the two.

Unquoted attribute value syntax

The attribute name, followed by zero or more space characters, followed by a single U+003D EQUALS SIGN character, followed by zero or more space characters, followed by the attribute value, which, in addition to the requirements given above for attribute values, must not contain any literal space characters, any U+0022 QUOTATION MARK characters ("), U+0027 APOSTROPHE characters ('), U+003D EQUALS SIGN characters (=), U+003C LESS-THAN SIGN characters (<), U+003E GREATER-THAN SIGN characters (>), or U+0060 GRAVE ACCENT characters (`), and must not be the empty string.

In the following example, the value attribute is given with the unquoted attribute value syntax:

<input value=yes>

If an attribute using the unquoted attribute syntax is to be followed by another attribute or by the optional U+002F SOLIDUS character (/) allowed in step 6 of the start tag syntax above, then there must be a space character separating the two.

Single-quoted attribute value syntax

The attribute name, followed by zero or more space characters, followed by a single U+003D EQUALS SIGN character, followed by zero or more space characters, followed by a single U+0027 APOSTROPHE character ('), followed by the attribute value, which, in addition to the requirements given above for attribute values, must not contain any literal U+0027 APOSTROPHE characters ('), and finally followed by a second single U+0027 APOSTROPHE character (').

In the following example, the type attribute is given with the single-quoted attribute value syntax:

<input type='checkbox'>

If an attribute using the single-quoted attribute syntax is to be followed by another attribute, then there must be a space character separating the two.

Double-quoted attribute value syntax

The attribute name, followed by zero or more space characters, followed by a single U+003D EQUALS SIGN character, followed by zero or more space characters, followed by a single U+0022 QUOTATION MARK character ("), followed by the attribute value, which, in addition to the requirements given above for attribute values, must not contain any literal U+0022 QUOTATION MARK characters ("), and finally followed by a second single U+0022 QUOTATION MARK character (").

In the following example, the name attribute is given with the double-quoted attribute value syntax:

<input name="be evil">

If an attribute using the double-quoted attribute syntax is to be followed by another attribute, then there must be a space character separating the two.

There must never be two or more attributes on the same start tag whose names are an ASCII case-insensitive match for each other.

When a foreign element has one of the namespaced attributes given by the local name and namespace of the first and second cells of a row from the following table, it must be written using the name given by the third cell from the same row.

Local name	Namespace	Attribute name
`actuate`	XLink namespace	`xlink:actuate`
`arcrole`	XLink namespace	`xlink:arcrole`
`href`	XLink namespace	`xlink:href`
`role`	XLink namespace	`xlink:role`
`show`	XLink namespace	`xlink:show`
`title`	XLink namespace	`xlink:title`
`type`	XLink namespace	`xlink:type`
`base`	XML namespace	`xml:base`
`lang`	XML namespace	`xml:lang`
`space`	XML namespace	`xml:space`
`xmlns`	XMLNS namespace	`xmlns`
`xlink`	XMLNS namespace	`xmlns:xlink`

No other namespaced attribute can be expressed in the HTML syntax.

8.1.2.4 Optional tags

Status: Last call for comments

Certain tags can be omitted.

Omitting an element's start tag does not mean the element is not present; it is implied, but it is still there. An HTML document always has a root html element, even if the string <html> doesn't appear anywhere in the markup.

An html element's start tag may be omitted if the first thing inside the html element is not a comment.

An html element's end tag may be omitted if the html element is not immediately followed by a comment.

A head element's start tag may be omitted if the element is empty, or if the first thing inside the head element is an element.

A head element's end tag may be omitted if the head element is not immediately followed by a space character or a comment.

A body element's start tag may be omitted if the element is empty, or if the first thing inside the body element is not a space character or a comment, except if the first thing inside the body element is a script or style element.

A body element's end tag may be omitted if the body element is not immediately followed by a comment.

A li element's end tag may be omitted if the li element is immediately followed by another li element or if there is no more content in the parent element.

A dt element's end tag may be omitted if the dt element is immediately followed by another dt element or a dd element.

A dd element's end tag may be omitted if the dd element is immediately followed by another dd element or a dt element, or if there is no more content in the parent element.

A p element's end tag may be omitted if the p element is immediately followed by an address, article, aside, blockquote, dir, div, dl, fieldset, footer, form, h1, h2, h3, h4, h5, h6, header, hgroup, hr, menu, nav, ol, p, pre, section, table, or ul, element, or if there is no more content in the parent element and the parent element is not an a element.

An rt element's end tag may be omitted if the rt element is immediately followed by an rt or rp element, or if there is no more content in the parent element.

An rp element's end tag may be omitted if the rp element is immediately followed by an rt or rp element, or if there is no more content in the parent element.

An optgroup element's end tag may be omitted if the optgroup element is immediately followed by another optgroup element, or if there is no more content in the parent element.

An option element's end tag may be omitted if the option element is immediately followed by another option element, or if it is immediately followed by an optgroup element, or if there is no more content in the parent element.

A colgroup element's start tag may be omitted if the first thing inside the colgroup element is a col element, and if the element is not immediately preceded by another colgroup element whose end tag has been omitted. (It can't be omitted if the element is empty.)

A colgroup element's end tag may be omitted if the colgroup element is not immediately followed by a space character or a comment.

A thead element's end tag may be omitted if the thead element is immediately followed by a tbody or tfoot element.

A tbody element's start tag may be omitted if the first thing inside the tbody element is a tr element, and if the element is not immediately preceded by a tbody, thead, or tfoot element whose end tag has been omitted. (It can't be omitted if the element is empty.)

A tbody element's end tag may be omitted if the tbody element is immediately followed by a tbody or tfoot element, or if there is no more content in the parent element.

A tfoot element's end tag may be omitted if the tfoot element is immediately followed by a tbody element, or if there is no more content in the parent element.

A tr element's end tag may be omitted if the tr element is immediately followed by another tr element, or if there is no more content in the parent element.

A td element's end tag may be omitted if the td element is immediately followed by a td or th element, or if there is no more content in the parent element.

A th element's end tag may be omitted if the th element is immediately followed by a td or th element, or if there is no more content in the parent element.

However, a start tag must never be omitted if it has any attributes.

8.1.2.5 Restrictions on content models

Status: Last call for comments

For historical reasons, certain elements have extra restrictions beyond even the restrictions given by their content model.

A table element must not contain tr elements, even though these elements are technically allowed inside table elements according to the content models described in this specification. (If a tr element is put inside a table in the markup, it will in fact imply a tbody start tag before it.)

A single newline may be placed immediately after the start tag of pre and textarea elements. This does not affect the processing of the element. The otherwise optional newline must be included if the element's contents themselves start with a newline (because otherwise the leading newline in the contents would be treated like the optional newline, and ignored).

The following two pre blocks are equivalent:

<pre>Hello</pre>

<pre>
Hello</pre>

8.1.2.6 Restrictions on the contents of raw text and RCDATA elements

Status: Last call for comments

The text in raw text and RCDATAs element must not contain any occurrences of the string "</" (U+003C LESS-THAN SIGN, U+002F SOLIDUS) followed by characters that case-insensitively match the tag name of the element followed by one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), U+0020 SPACE, U+003E GREATER-THAN SIGN (>), or U+002F SOLIDUS (/).

8.1.3 Text

Status: Last call for comments

Text is allowed inside elements, attributes, and comments. Text must consist of Unicode characters. Text must not contain U+0000 characters. Text must not contain permanently undefined Unicode characters (noncharacters). Text must not contain control characters other than space characters. Extra constraints are placed on what is and what is not allowed in text based on where the text is to be put, as described in the other sections.

8.1.3.1 Newlines

Status: Last call for comments

Newlines in HTML may be represented either as U+000D CARRIAGE RETURN (CR) characters, U+000A LINE FEED (LF) characters, or pairs of U+000D CARRIAGE RETURN (CR), U+000A LINE FEED (LF) characters in that order.

8.1.4 Character references

Status: Last call for comments

In certain cases described in other sections, text may be mixed with character references. These can be used to escape characters that couldn't otherwise legally be included in text.

Character references must start with a U+0026 AMPERSAND character (&). Following this, there are three possible kinds of character references:

Named character references: The ampersand must be followed by one of the names given in the named character references section, using the same case. The name must be one that is terminated by a U+003B SEMICOLON character (;).
Decimal numeric character reference: The ampersand must be followed by a U+0023 NUMBER SIGN character (#), followed by one or more digits in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), representing a base-ten integer that corresponds to a Unicode code point that is allowed according to the definition below. The digits must then be followed by a U+003B SEMICOLON character (;).
Hexadecimal numeric character reference: The ampersand must be followed by a U+0023 NUMBER SIGN character (#), which must be followed by either a U+0078 LATIN SMALL LETTER X character (x) or a U+0058 LATIN CAPITAL LETTER X character (X), which must then be followed by one or more digits in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), U+0061 LATIN SMALL LETTER A to U+0066 LATIN SMALL LETTER F, and U+0041 LATIN CAPITAL LETTER A to U+0046 LATIN CAPITAL LETTER F, representing a base-sixteen integer that corresponds to a Unicode code point that is allowed according to the definition below. The digits must then be followed by a U+003B SEMICOLON character (;).

The numeric character reference forms described above are allowed to reference any Unicode code point other than U+0000, permanently undefined Unicode characters (noncharacters), and control characters other than space characters.

An ambiguous ampersand is a U+0026 AMPERSAND character (&) that is followed by some text other than a space character, a U+003C LESS-THAN SIGN character (<), or another U+0026 AMPERSAND character (&).

8.1.5 CDATA sections

Status: Last call for comments

CDATA sections must start with the character sequence U+003C LESS-THAN SIGN, U+0021 EXCLAMATION MARK, U+005B LEFT SQUARE BRACKET, U+0043 LATIN CAPITAL LETTER C, U+0044 LATIN CAPITAL LETTER D, U+0041 LATIN CAPITAL LETTER A, U+0054 LATIN CAPITAL LETTER T, U+0041 LATIN CAPITAL LETTER A, U+005B LEFT SQUARE BRACKET (<![CDATA[). Following this sequence, the CDATA section may have text, with the additional restriction that the text must not contain the three character sequence U+005D RIGHT SQUARE BRACKET, U+005D RIGHT SQUARE BRACKET, U+003E GREATER-THAN SIGN (]]>). Finally, the CDATA section must be ended by the three character sequence U+005D RIGHT SQUARE BRACKET, U+005D RIGHT SQUARE BRACKET, U+003E GREATER-THAN SIGN (]]>).

CDATA sections can only be used in foreign content (MathML or SVG). In this example, a CDATA section is used to escape the contents of an ms element:

<p>You can add a string to a number, but this stringifies the number:</p>
<math>
 <ms><![CDATA[x<y]]></ms>
 <mo>+</mo>
 <mn>3</mn>
 <mo>=</mo>
 <ms><![CDATA[x<y3]]></ms>
</math>

8.1.6 Comments

Status: Last call for comments

Comments must start with the four character sequence U+003C LESS-THAN SIGN, U+0021 EXCLAMATION MARK, U+002D HYPHEN-MINUS, U+002D HYPHEN-MINUS ().

8.2 Parsing HTML documents

Status: Last call for comments

This section only applies to user agents, data mining tools, and conformance checkers.

The rules for parsing XML documents into DOM trees are covered by the next section, entitled "The XHTML syntax".

For HTML documents, user agents must use the parsing rules described in this section to generate the DOM trees. Together, these rules define what is referred to as the HTML parser.

While the HTML syntax described in this specification bears a close resemblance to SGML and XML, it is a separate language with its own parsing rules.

Some earlier versions of HTML (in particular from HTML2 to HTML4) were based on SGML and used SGML parsing rules. However, few (if any) web browsers ever implemented true SGML parsing for HTML documents; the only user agents to strictly handle HTML as an SGML application have historically been validators. The resulting confusion — with validators claiming documents to have one representation while widely deployed Web browsers interoperably implemented a different representation — has wasted decades of productivity. This version of HTML thus returns to a non-SGML basis.

Authors interested in using SGML tools in their authoring pipeline are encouraged to use XML tools and the XML serialization of HTML.

This specification defines the parsing rules for HTML documents, whether they are syntactically correct or not. Certain points in the parsing algorithm are said to be parse errors. The error handling for parse errors is well-defined: user agents must either act as described below when encountering such problems, or must abort processing at the first error that they encounter for which they do not wish to apply the rules described below.

Conformance checkers must report at least one parse error condition to the user if one or more parse error conditions exist in the document and must not report parse error conditions if none exist in the document. Conformance checkers may report more than one parse error condition if more than one parse error condition exists in the document. Conformance checkers are not required to recover from parse errors.

Parse errors are only errors with the syntax of HTML. In addition to checking for parse errors, conformance checkers will also verify that the document obeys all the other conformance requirements described in this specification.

For the purposes of conformance checkers, if a resource is determined to be in the HTML syntax, then it is an HTML document.

8.2.1 Overview of the parsing model

Status: Last call for comments

The input to the HTML parsing process consists of a stream of Unicode characters, which is passed through a tokenization stage followed by a tree construction stage. The output is a Document object.

Implementations that do not support scripting do not have to actually create a DOM Document object, but the DOM tree in such cases is still used as the model for the rest of the specification.

In the common case, the data handled by the tokenization stage comes from the network, but it can also come from script, e.g. using the document.write() API.

There is only one set of states for the tokenizer stage and the tree construction stage, but the tree construction stage is reentrant, meaning that while the tree construction stage is handling one token, the tokenizer might be resumed, causing further tokens to be emitted and processed before the first token's processing is complete.

In the following example, the tree construction stage will be called upon to handle a "p" start tag token while handling the "script" start tag token:

...
<script>
 document.write('<p>');
</script>
...

To handle these cases, parsers have a script nesting level, which must be initially set to zero, and a parser pause flag, which must be initially set to false.

8.2.2 The input stream

Status: Last call for comments

The stream of Unicode characters that comprises the input to the tokenization stage will be initially seen by the user agent as a stream of bytes (typically coming over the network or from the local file system). The bytes encode the actual characters according to a particular character encoding, which the user agent must use to decode the bytes into characters.

For XML documents, the algorithm user agents must use to determine the character encoding is given by the XML specification. This section does not apply to XML documents. [XML]

8.2.2.1 Determining the character encoding

Status: Last call for comments

In some cases, it might be impractical to unambiguously determine the encoding before parsing the document. Because of this, this specification provides for a two-pass mechanism with an optional pre-scan. Implementations are allowed, as described below, to apply a simplified parsing algorithm to whatever bytes they have available before beginning to parse the document. Then, the real parser is started, using a tentative encoding derived from this pre-parse and other out-of-band metadata. If, while the document is being loaded, the user agent discovers an encoding declaration that conflicts with this information, then the parser can get reinvoked to perform a parse of the document with the real encoding.

User agents must use the following algorithm (the encoding sniffing algorithm) to determine the character encoding to use when decoding a document in the first pass. This algorithm takes as input any out-of-band metadata available to the user agent (e.g. the Content-Type metadata of the document) and all the bytes available so far, and returns an encoding and a confidence. The confidence is either tentative, certain, or irrelevant. The encoding used, and whether the confidence in that encoding is tentative or certain, is used during the parsing to determine whether to change the encoding. If no encoding is necessary, e.g. because the parser is operating on a stream of Unicode characters and doesn't have to use an encoding at all, then the confidence is irrelevant.

If the transport layer specifies an encoding, and it is supported, return that encoding with the confidence certain, and abort these steps.
The user agent may wait for more bytes of the resource to be available, either in this step or at any later step in this algorithm. For instance, a user agent might wait 500ms or 512 bytes, whichever came first. In general preparsing the source to find the encoding improves performance, as it reduces the need to throw away the data structures used when parsing upon finding the encoding information. However, if the user agent delays too long to obtain data to determine the encoding, then the cost of the delay could outweigh any performance improvements from the preparse.
For each of the rows in the following table, starting with the first one and going down, if there are as many or more bytes available than the number of bytes in the first column, and the first bytes of the file match the bytes given in the first column, then return the encoding given in the cell in the second column of that row, with the confidence certain, and abort these steps:

Bytes in Hexadecimal Encoding
FE FF UTF-16BE
FF FE UTF-16LE
EF BB BF UTF-8
This step looks for Unicode Byte Order Marks (BOMs).
Otherwise, the user agent will have to search for explicit character encoding information in the file itself. This should proceed as follows:
Let position be a pointer to a byte in the input stream, initially pointing at the first byte. If at any point during these substeps the user agent either runs out of bytes or decides that scanning further bytes would not be efficient, then skip to the next step of the overall character encoding detection algorithm. User agents may decide that scanning any bytes is not efficient, in which case these substeps are entirely skipped.

Now, repeat the following "two" steps until the algorithm aborts (either because user agent aborts, as described above, or because a character encoding is found):
1. If position points to:
  A sequence of bytes starting with: 0x3C 0x21 0x2D 0x2D (ASCII '' sequence) and comes after the 0x3C byte that was found. (The two 0x2D bytes can be the same as the those in the '<!--' sequence.)
  
  A sequence of bytes starting with: 0x3C, 0x4D or 0x6D, 0x45 or 0x65, 0x54 or 0x74, 0x41 or 0x61, and finally one of 0x09, 0x0A, 0x0C, 0x0D, 0x20, 0x2F (case-insensitive ASCII '<meta' followed by a space or slash)
  1. Advance the position pointer so that it points at the next 0x09, 0x0A, 0x0C, 0x0D, 0x20, or 0x2F byte (the one in sequence of characters matched above).
  2. Get an attribute and its value. If no attribute was sniffed, then skip this inner set of steps, and jump to the second step in the overall "two step" algorithm.
  3. If the attribute's name is neither "charset" nor "content", then return to step 2 in these inner steps.
  4. If the attribute's name is "charset", let charset be the attribute's value, interpreted as a character encoding.
  5. Otherwise, the attribute's name is "content": apply the algorithm for extracting an encoding from a Content-Type, giving the attribute's value as the string to parse. If an encoding is returned, let charset be that encoding. Otherwise, return to step 2 in these inner steps.
  6. If charset is a UTF-16 encoding, change the value of charset to UTF-8.
  7. If charset is a supported character encoding, then return the given encoding, with confidence tentative, and abort all these steps.
  8. Otherwise, return to step 2 in these inner steps.
  A sequence of bytes starting with a 0x3C byte (ASCII <), optionally a 0x2F byte (ASCII /), and finally a byte in the range 0x41-0x5A or 0x61-0x7A (an ASCII letter)
  1. Advance the position pointer so that it points at the next 0x09 (ASCII TAB), 0x0A (ASCII LF), 0x0C (ASCII FF), 0x0D (ASCII CR), 0x20 (ASCII space), or 0x3E (ASCII >) byte.
  2. Repeatedly get an attribute until no further attributes can be found, then jump to the second step in the overall "two step" algorithm.
  A sequence of bytes starting with: 0x3C 0x21 (ASCII '<!')
  
  A sequence of bytes starting with: 0x3C 0x2F (ASCII '</')
  
  A sequence of bytes starting with: 0x3C 0x3F (ASCII '<?')
  
  Advance the position pointer so that it points at the first 0x3E byte (ASCII >) that comes after the 0x3C byte that was found.
  
  Any other byte
  
  Do nothing with that byte.
2. Move position so it points at the next byte in the input stream, and return to the first step of this "two step" algorithm.
When the above "two step" algorithm says to get an attribute, it means doing this:
1. If the byte at position is one of 0x09 (ASCII TAB), 0x0A (ASCII LF), 0x0C (ASCII FF), 0x0D (ASCII CR), 0x20 (ASCII space), or 0x2F (ASCII /) then advance position to the next byte and redo this substep.
2. If the byte at position is 0x3E (ASCII >), then abort the "get an attribute" algorithm. There isn't one.
3. Otherwise, the byte at position is the start of the attribute name. Let attribute name and attribute value be the empty string.
4. Attribute name: Process the byte at position as follows:
  
  If it is 0x3D (ASCII =), and the attribute name is longer than the empty string
  
  Advance position to the next byte and jump to the step below labeled value.
  
  If it is 0x09 (ASCII TAB), 0x0A (ASCII LF), 0x0C (ASCII FF), 0x0D (ASCII CR), or 0x20 (ASCII space)
  
  Jump to the step below labeled spaces.
  
  If it is 0x2F (ASCII /) or 0x3E (ASCII >)
  
  Abort the "get an attribute" algorithm. The attribute's name is the value of attribute name, its value is the empty string.
  
  If it is in the range 0x41 (ASCII A) to 0x5A (ASCII Z)
  
  Append the Unicode character with code point b+0x20 to attribute name (where b is the value of the byte at position).
  
  Anything else
  
  Append the Unicode character with the same code point as the value of the byte at position) to attribute name. (It doesn't actually matter how bytes outside the ASCII range are handled here, since only ASCII characters can contribute to the detection of a character encoding.)
5. Advance position to the next byte and return to the previous step.
6. Spaces: If the byte at position is one of 0x09 (ASCII TAB), 0x0A (ASCII LF), 0x0C (ASCII FF), 0x0D (ASCII CR), or 0x20 (ASCII space) then advance position to the next byte, then, repeat this step.
7. If the byte at position is not 0x3D (ASCII =), abort the "get an attribute" algorithm. The attribute's name is the value of attribute name, its value is the empty string.
8. Advance position past the 0x3D (ASCII =) byte.
9. Value: If the byte at position is one of 0x09 (ASCII TAB), 0x0A (ASCII LF), 0x0C (ASCII FF), 0x0D (ASCII CR), or 0x20 (ASCII space) then advance position to the next byte, then, repeat this step.
10. Process the byte at position as follows:
  If it is 0x22 (ASCII ") or 0x27 (ASCII ')
  1. Let b be the value of the byte at position.
  2. Advance position to the next byte.
  3. If the value of the byte at position is the value of b, then advance position to the next byte and abort the "get an attribute" algorithm. The attribute's name is the value of attribute name, and its value is the value of attribute value.
  4. Otherwise, if the value of the byte at position is in the range 0x41 (ASCII A) to 0x5A (ASCII Z), then append a Unicode character to attribute value whose code point is 0x20 more than the value of the byte at position.
  5. Otherwise, append a Unicode character to attribute value whose code point is the same as the value of the byte at position.
  6. Return to the second step in these substeps.
  If it is 0x3E (ASCII >)
  
  Abort the "get an attribute" algorithm. The attribute's name is the value of attribute name, its value is the empty string.
  
  If it is in the range 0x41 (ASCII A) to 0x5A (ASCII Z)
  
  Append the Unicode character with code point b+0x20 to attribute value (where b is the value of the byte at position). Advance position to the next byte.
  
  Anything else
  
  Append the Unicode character with the same code point as the value of the byte at position) to attribute value. Advance position to the next byte.
11. Process the byte at position as follows:
  
  If it is 0x09 (ASCII TAB), 0x0A (ASCII LF), 0x0C (ASCII FF), 0x0D (ASCII CR), 0x20 (ASCII space), or 0x3E (ASCII >)
  
  Abort the "get an attribute" algorithm. The attribute's name is the value of attribute name and its value is the value of attribute value.
  
  If it is in the range 0x41 (ASCII A) to 0x5A (ASCII Z)
  
  Append the Unicode character with code point b+0x20 to attribute value (where b is the value of the byte at position).
  
  Anything else
  
  Append the Unicode character with the same code point as the value of the byte at position) to attribute value.
12. Advance position to the next byte and return to the previous step.
For the sake of interoperability, user agents should not use a pre-scan algorithm that returns different results than the one described above. (But, if you do, please at least let us know, so that we can improve this algorithm and benefit everyone...)
If the user agent has information on the likely encoding for this page, e.g. based on the encoding of the page when it was last visited, then return that encoding, with the confidence tentative, and abort these steps.
The user agent may attempt to autodetect the character encoding from applying frequency analysis or other algorithms to the data stream. Such algorithms may use information about the resource other than the resource's contents, including the address of the resource. If autodetection succeeds in determining a character encoding, then return that encoding, with the confidence tentative, and abort these steps. [UNIVCHARDET]

The UTF-8 encoding has a highly detectable bit pattern. Documents that contain bytes with values greater than 0x7F which match the UTF-8 pattern are very likely to be UTF-8, while documents with byte sequences that do not match it are very likely not. User-agents are therefore encouraged to search for this common encoding. [PPUTF8] [UTF8DET]

Bytes in Hexadecimal	Encoding
FE FF	UTF-16BE
FF FE	UTF-16LE
EF BB BF	UTF-8

Otherwise, return an implementation-defined or user-specified default character encoding, with the confidence tentative.

In controlled environments or in environments where the encoding of documents can be prescribed (for example, for user agents intended for dedicated use in new networks), the comprehensive UTF-8 encoding is suggested.

In other environments, the default encoding is typically dependent on the user's locale (an approximation of the languages, and thus often encodings, of the pages that the user is likely to frequent). The following table gives suggested defaults based on the user's locale, for compatibility with legacy content. Locales are identified by BCP 47 language codes. [BCP47]

Locale language	Suggested default encoding
ar	UTF-8
be	ISO-8859-5
bg	windows-1251
cs	ISO-8859-2
cy	UTF-8
fa	UTF-8
he	windows-1255
hr	UTF-8
hu	ISO-8859-2
ja	Windows-31J
kk	UTF-8
ko	windows-949
ku	windows-1254
lt	windows-1257
lv	ISO-8859-13
mk	UTF-8
or	UTF-8
pl	ISO-8859-2
ro	UTF-8
ru	windows-1251
sk	windows-1250
sl	ISO-8859-2
sr	UTF-8
th	windows-874
tr	windows-1254
uk	windows-1251
vi	UTF-8
zh-CN	GB18030
zh-TW	Big5
All other locales	windows-1252

The document's character encoding must immediately be set to the value returned from this algorithm, at the same time as the user agent uses the returned value to select the decoder to use for the input stream.

This algorithm is a willful violation of the HTTP specification, which requires that the encoding be assumed to be ISO-8859-1 in the absence of a character encoding declaration to the contrary, and of RFC 2046, which requires that the encoding be assumed to be US-ASCII in the absence of a character encoding declaration to the contrary. This specification's third approach is motivated by a desire to be maximally compatible with legacy content. [HTTP] [RFC2046]

8.2.2.2 Character encodings

Status: Last call for comments

User agents must at a minimum support the UTF-8 and Windows-1252 encodings, but may support more.

It is not unusual for Web browsers to support dozens if not upwards of a hundred distinct character encodings.

User agents must support the preferred MIME name of every character encoding they support, and should support all the IANA-registered names and aliases of every character encoding they support. [IANACHARSET]

When comparing a string specifying a character encoding with the name or alias of a character encoding to determine if they are equal, user agents must remove any leading or trailing space characters in both names, and then perform the comparison in an ASCII case-insensitive manner.

When a user agent would otherwise use an encoding given in the first column of the following table to either convert content to Unicode characters or convert Unicode characters to bytes, it must instead use the encoding given in the cell in the second column of the same row. When a byte or sequence of bytes is treated differently due to this encoding aliasing, it is said to have been misinterpreted for compatibility.

Character encoding overrides
Input encoding	Replacement encoding	References
EUC-KR	windows-949	[EUCKR] [WIN949]
GB2312	GBK	[RFC1345] [GBK]
GB_2312-80	GBK	[RFC1345] [GBK]
ISO-8859-1	windows-1252	[RFC1345] [WIN1252]
ISO-8859-9	windows-1254	[RFC1345] [WIN1254]
ISO-8859-11	windows-874	[ISO885911] [WIN874]
KS_C_5601-1987	windows-949	[RFC1345] [WIN949]
Shift_JIS	Windows-31J	[SHIFTJIS] [WIN31J]
TIS-620	windows-874	[TIS620] [WIN874]
US-ASCII	windows-1252	[RFC1345] [WIN1252]

The requirement to treat certain encodings as other encodings according to the table above is a willful violation of the W3C Character Model specification, motivated by a desire for compatibility with legacy content. [CHARMOD]

When a user agent is to use the UTF-16 encoding but no BOM has been found, user agents must default to UTF-16LE.

The requirement to default UTF-16 to LE rather than BE is a willful violation of RFC 2781, motivated by a desire for compatibility with legacy content. [RFC2781]

User agents must not support the CESU-8, UTF-7, BOCU-1 and SCSU encodings. [CESU8] [UTF7] [BOCU1] [SCSU]

Support for encodings based on EBCDIC is not recommended. This encoding is rarely used for publicly-facing Web content.

Support for UTF-32 is not recommended. This encoding is rarely used, and frequently implemented incorrectly.

This specification does not make any attempt to support EBCDIC-based encodings and UTF-32 in its algorithms; support and use of these encodings can thus lead to unexpected behavior in implementations of this specification.

8.2.2.3 Preprocessing the input stream

Status: Last call for comments

Given an encoding, the bytes in the input stream must be converted to Unicode characters for the tokenizer, as described by the rules for that encoding, except that the leading U+FEFF BYTE ORDER MARK character, if any, must not be stripped by the encoding layer (it is stripped by the rule below).

Bytes or sequences of bytes in the original byte stream that could not be converted to Unicode code points must be converted to U+FFFD REPLACEMENT CHARACTERs.

Bytes or sequences of bytes in the original byte stream that did not conform to the encoding specification (e.g. invalid UTF-8 byte sequences in a UTF-8 input stream) are errors that conformance checkers are expected to report.

Any byte or sequence of bytes in the original byte stream that is misinterpreted for compatibility is a parse error.

One leading U+FEFF BYTE ORDER MARK character must be ignored if any are present.

The requirement to strip a U+FEFF BYTE ORDER MARK character regardless of whether that character was used to determine the byte order is a willful violation of Unicode, motivated by a desire to increase the resilience of user agents in the face of naïve transcoders.

All U+0000 NULL characters and code points in the range U+D800 to U+DFFF in the input must be replaced by U+FFFD REPLACEMENT CHARACTERs. Any occurrences of such characters and code points are parse errors.

Any occurrences of any characters in the ranges U+0001 to U+0008, U+000E to U+001F, U+007F to U+009F, U+FDD0 to U+FDEF, and characters U+000B, U+FFFE, U+FFFF, U+1FFFE, U+1FFFF, U+2FFFE, U+2FFFF, U+3FFFE, U+3FFFF, U+4FFFE, U+4FFFF, U+5FFFE, U+5FFFF, U+6FFFE, U+6FFFF, U+7FFFE, U+7FFFF, U+8FFFE, U+8FFFF, U+9FFFE, U+9FFFF, U+AFFFE, U+AFFFF, U+BFFFE, U+BFFFF, U+CFFFE, U+CFFFF, U+DFFFE, U+DFFFF, U+EFFFE, U+EFFFF, U+FFFFE, U+FFFFF, U+10FFFE, and U+10FFFF are parse errors. These are all control characters or permanently undefined Unicode characters (noncharacters).

U+000D CARRIAGE RETURN (CR) characters and U+000A LINE FEED (LF) characters are treated specially. Any CR characters that are followed by LF characters must be removed, and any CR characters not followed by LF characters must be converted to LF characters. Thus, newlines in HTML DOMs are represented by LF characters, and there are never any CR characters in the input to the tokenization stage.

The next input character is the first character in the input stream that has not yet been consumed. Initially, the next input character is the first character in the input. The current input character is the last character to have been consumed.

The insertion point is the position (just before a character or just before the end of the input stream) where content inserted using document.write() is actually inserted. The insertion point is relative to the position of the character immediately after it, it is not an absolute offset into the input stream. Initially, the insertion point is undefined.

The "EOF" character in the tables below is a conceptual character representing the end of the input stream. If the parser is a script-created parser, then the end of the input stream is reached when an explicit "EOF" character (inserted by the document.close() method) is consumed. Otherwise, the "EOF" character is not a real character in the stream, but rather the lack of any further characters.

8.2.2.4 Changing the encoding while parsing

Status: Last call for comments

When the parser requires the user agent to change the encoding, it must run the following steps. This might happen if the encoding sniffing algorithm described above failed to find an encoding, or if it found an encoding that was not the actual encoding of the file.

If the new encoding is identical or equivalent to the encoding that is already being used to interpret the input stream, then set the confidence to certain and abort these steps. This happens when the encoding information found in the file matches what the encoding sniffing algorithm determined to be the encoding, and in the second pass through the parser if the first pass found that the encoding sniffing algorithm described in the earlier section failed to find the right encoding.
If the encoding that is already being used to interpret the input stream is a UTF-16 encoding, then set the confidence to certain and abort these steps. The new encoding is ignored; if it was anything but the same encoding, then it would be clearly incorrect.
If the new encoding is a UTF-16 encoding, change it to UTF-8.
If all the bytes up to the last byte converted by the current decoder have the same Unicode interpretations in both the current encoding and the new encoding, and if the user agent supports changing the converter on the fly, then the user agent may change to the new converter for the encoding on the fly. Set the document's character encoding and the encoding used to convert the input stream to the new encoding, set the confidence to certain, and abort these steps.
Otherwise, navigate to the document again, with replacement enabled, and using the same source browsing context, but this time skip the encoding sniffing algorithm and instead just set the encoding to the new encoding and the confidence to certain. Whenever possible, this should be done without actually contacting the network layer (the bytes should be re-parsed from memory), even if, e.g., the document is marked as not being cacheable. If this is not possible and contacting the network layer would involve repeating a request that uses a method other than HTTP GET (or equivalent for non-HTTP URLs), then instead set the confidence to certain and ignore the new encoding. The resource will be misinterpreted. User agents may notify the user of the situation, to aid in application development.

8.2.3 Parse state

Status: Last call for comments

8.2.3.1 The insertion mode

Status: Last call for comments

The insertion mode is a state variable that controls the primary operation of the tree construction stage.

Initially, the insertion mode is "initial". It can change to "before html", "before head", "in head", "in head noscript", "after head", "in body", "text", "in table", "in table text", "in caption", "in column group", "in table body", "in row", "in cell", "in select", "in select in table", "in foreign content", "after body", "in frameset", "after frameset", "after after body", and "after after frameset" during the course of the parsing, as described in the tree construction stage. The insertion mode affects how tokens are processed and whether CDATA sections are supported.

Seven of these modes, namely "in head", "in body", "in table", "in table body", "in row", "in cell", and "in select", are special, in that the other modes defer to them at various times. When the algorithm below says that the user agent is to do something "using the rules for the m insertion mode", where m is one of these modes, the user agent must use the rules described under the m insertion mode's section, but must leave the insertion mode unchanged unless the rules in m themselves switch the insertion mode to a new value.

When the insertion mode is switched to "text" or "in table text", the original insertion mode is also set. This is the insertion mode to which the tree construction stage will return.

When the insertion mode is switched to "in foreign content", the secondary insertion mode is also set. This secondary mode is used within the rules for the "in foreign content" mode to handle HTML (i.e. not foreign) content.

When the steps below require the UA to reset the insertion mode appropriately, it means the UA must follow these steps:

Let last be false.
Let foreign be false.
Let node be the last node in the stack of open elements.
Loop: If node is the first node in the stack of open elements, then set last to true and set node to the context element. (fragment case)
If node is a select element, then switch the insertion mode to "in select" and jump to the step labeled end. (fragment case)
If node is a td or th element and last is false, then switch the insertion mode to "in cell" and jump to the step labeled end.
If node is a tr element, then switch the insertion mode to "in row" and jump to the step labeled end.
If node is a tbody, thead, or tfoot element, then switch the insertion mode to "in table body" and jump to the step labeled end.
If node is a caption element, then switch the insertion mode to "in caption" and jump to the step labeled end.
If node is a colgroup element, then switch the insertion mode to "in column group" and jump to the step labeled end. (fragment case)
If node is a table element, then switch the insertion mode to "in table" and jump to the step labeled end.
If node is a head element, then switch the insertion mode to "in body" ("in body"! not "in head"!) and jump to the step labeled end. (fragment case)
If node is a body element, then switch the insertion mode to "in body" and jump to the step labeled end.
If node is a frameset element, then switch the insertion mode to "in frameset" and jump to the step labeled end. (fragment case)
If node is an html element, then switch the insertion mode to "before head" Then, jump to the step labeled end. (fragment case)
If node is an element from the MathML namespace or the SVG namespace, then set the foreign flag to true.
If last is true, then switch the insertion mode to "in body" and jump to the step labeled end. (fragment case)
Let node now be the node before node in the stack of open elements.
Return to the step labeled loop.
End: If foreign is true, switch the secondary insertion mode to whatever the insertion mode is set to, and switch the insertion mode to "in foreign content".

8.2.3.2 The stack of open elements

Status: Last call for comments

Initially, the stack of open elements is empty. The stack grows downwards; the topmost node on the stack is the first one added to the stack, and the bottommost node of the stack is the most recently added node in the stack (notwithstanding when the stack is manipulated in a random access fashion as part of the handling for misnested tags).

The "before html" insertion mode creates the html root element node, which is then added to the stack.

In the fragment case, the stack of open elements is initialized to contain an html element that is created as part of that algorithm. (The fragment case skips the "before html" insertion mode.)

The html node, however it is created, is the topmost node of the stack. It only gets popped off the stack when the parser finishes.

The current node is the bottommost node in this stack.

The current table is the last table element in the stack of open elements, if there is one. If there is no table element in the stack of open elements (fragment case), then the current table is the first element in the stack of open elements (the html element).

Elements in the stack fall into the following categories:

Special: The following HTML elements have varying levels of special parsing rules: address, area, article, aside, base, basefont, bgsound, blockquote, body, br, center, col, colgroup, command, , dd, details, dir, div, dl, dt, embed, fieldset, figure, footer, form, frame, frameset, h1, h2, h3, h4, h5, h6, head, header, hgroup, hr, iframe, img, input, isindex, li, link, listing, menu, meta, nav, noembed, noframes, noscript, ol, p, param, plaintext, pre, script, section, select, style, tbody, textarea, tfoot, thead, title, tr, ul, wbr, and xmp.
Scoping: The following HTML elements introduce new scopes for various parts of the parsing: applet, button, caption, html, marquee, object, table, td, th, and SVG's foreignObject.
Formatting: The following HTML elements are those that end up in the list of active formatting elements: a, b, big, code, em, font, i, nobr, s, small, strike, strong, tt, and u.
Phrasing: All other elements found while parsing an HTML document.

The stack of open elements is said to have an element in a specific scope consisting of a list of element types list when the following algorithm terminates in a match state:

Initialize node to be the current node (the bottommost node of the stack).
If node is the target node, terminate in a match state.
Otherwise, if node is one of the element types in list, terminate in a failure state.
Otherwise, set node to the previous entry in the stack of open elements and return to step 2. (This will never fail, since the loop will always terminate in the previous step if the top of the stack — an html element — is reached.)

The stack of open elements is said to have an element in scope when it has an element in the specific scope consisting of the following element types:

applet in the HTML namespace
caption in the HTML namespace
html in the HTML namespace
table in the HTML namespace
td in the HTML namespace
th in the HTML namespace
button in the HTML namespace
marquee in the HTML namespace
object in the HTML namespace
foreignObject in the SVG namespace

The stack of open elements is said to have an element in list item scope when it has an element in the specific scope consisting of the following element types:

All the element types listed above for the has an element in scope algorithm.
ol in the HTML namespace
ul in the HTML namespace

The stack of open elements is said to have an element in table scope when it has an element in the specific scope consisting of the following element types:

html in the HTML namespace
table in the HTML namespace

Nothing happens if at any time any of the elements in the stack of open elements are moved to a new location in, or removed from, the Document tree. In particular, the stack is not changed in this situation. This can cause, amongst other strange effects, content to be appended to nodes that are no longer in the DOM.

In some cases (namely, when closing misnested formatting elements), the stack is manipulated in a random-access fashion.

8.2.3.3 The list of active formatting elements

Status: Last call for comments

Initially, the list of active formatting elements is empty. It is used to handle mis-nested formatting element tags.

The list contains elements in the formatting category, and scope markers. The scope markers are inserted when entering applet elements, buttons, object elements, marquees, table cells, and table captions, and are used to prevent formatting from "leaking" into applet elements, buttons, object elements, marquees, and tables.

The scope markers are unrelated to the concept of an element being in scope.

In addition, each element in the list of active formatting elements is associated with the token for which it was created, so that further elements can be created for that token if necessary.

When the steps below require the UA to reconstruct the active formatting elements, the UA must perform the following steps:

If there are no entries in the list of active formatting elements, then there is nothing to reconstruct; stop this algorithm.
If the last (most recently added) entry in the list of active formatting elements is a marker, or if it is an element that is in the stack of open elements, then there is nothing to reconstruct; stop this algorithm.
Let entry be the last (most recently added) element in the list of active formatting elements.
If there are no entries before entry in the list of active formatting elements, then jump to step 8.
Let entry be the entry one earlier than entry in the list of active formatting elements.
If entry is neither a marker nor an element that is also in the stack of open elements, go to step 4.
Let entry be the element one later than entry in the list of active formatting elements.
Create an element for the token for which the element entry was created, to obtain new element.
Append new element to the current node and push it onto the stack of open elements so that it is the new current node.
Replace the entry for entry in the list with an entry for new element.
If the entry for new element in the list of active formatting elements is not the last entry in the list, return to step 7.

This has the effect of reopening all the formatting elements that were opened in the current body, cell, or caption (whichever is youngest) that haven't been explicitly closed.

The way this specification is written, the list of active formatting elements always consists of elements in chronological order with the least recently added element first and the most recently added element last (except for while steps 8 to 11 of the above algorithm are being executed, of course).

When the steps below require the UA to clear the list of active formatting elements up to the last marker, the UA must perform the following steps:

Let entry be the last (most recently added) entry in the list of active formatting elements.
Remove entry from the list of active formatting elements.
If entry was a marker, then stop the algorithm at this point. The list has been cleared up to the last marker.
Go to step 1.

8.2.3.4 The element pointers

Status: Last call for comments

Initially, the head element pointer and the form element pointer are both null.

Once a head element has been parsed (whether implicitly or explicitly) the head element pointer gets set to point to this node.

The form element pointer points to the last form element that was opened and whose end tag has not yet been seen. It is used to make form controls associate with forms in the face of dramatically bad markup, for historical reasons.

8.2.3.5 Other parsing state flags

Status: Last call for comments

The scripting flag is set to "enabled" if scripting was enabled for the Document with which the parser is associated when the parser was created, and "disabled" otherwise.

The scripting flag can be enabled even when the parser was originally created for the HTML fragment parsing algorithm, even though script elements don't execute in that case.

The frameset-ok flag is set to "ok" when the parser is created. It is set to "not ok" after certain tokens are seen.

8.2.4 Tokenization

Status: Last call for comments

Implementations must act as if they used the following state machine to tokenize HTML. The state machine must start in the data state. Most states consume a single character, which may have various side-effects, and either switches the state machine to a new state to reconsume the same character, or switches it to a new state (to consume the next character), or repeats the same state (to consume the next character). Some states have more complicated behavior and can consume several characters before switching to another state. In some cases, the tokenizer state is also changed by the tree construction stage.

The exact behavior of certain states depends on the insertion mode and the stack of open elements. Certain states also use a temporary buffer to track progress.

The output of the tokenization step is a series of zero or more of the following tokens: DOCTYPE, start tag, end tag, comment, character, end-of-file. DOCTYPE tokens have a name, a public identifier, a system identifier, and a force-quirks flag. When a DOCTYPE token is created, its name, public identifier, and system identifier must be marked as missing (which is a distinct state from the empty string), and the force-quirks flag must be set to off (its other state is on). Start and end tag tokens have a tag name, a self-closing flag, and a list of attributes, each of which has a name and a value. When a start or end tag token is created, its self-closing flag must be unset (its other state is that it be set), and its attributes list must be empty. Comment and character tokens have data.

When a token is emitted, it must immediately be handled by the tree construction stage. The tree construction stage can affect the state of the tokenization stage, and can insert additional characters into the stream. (For example, the script element can result in scripts executing and using the dynamic markup insertion APIs to insert characters into the stream being tokenized.)

When a start tag token is emitted with its self-closing flag set, if the flag is not acknowledged when it is processed by the tree construction stage, that is a parse error.

When an end tag token is emitted with attributes, that is a parse error.

When an end tag token is emitted with its self-closing flag set, that is a parse error.

An appropriate end tag token is an end tag token whose tag name matches the tag name of the last start tag to have been emitted from this tokenizer, if any. If no start tag has been emitted from this tokenizer, then no end tag token is appropriate.

Before each step of the tokenizer, the user agent must first check the parser pause flag. If it is true, then the tokenizer must abort the processing of any nested invocations of the tokenizer, yielding control back to the caller.

The tokenizer state machine consists of the states defined in the following subsections.

8.2.4.1 Data state

Status: Last call for comments

Consume the next input character:

U+0026 AMPERSAND (&): Switch to the character reference in data state.
U+003C LESS-THAN SIGN (<): Switch to the tag open state.
EOF: Emit an end-of-file token.
Anything else: Emit the current input character as a character token. Stay in the data state.

8.2.4.2 Character reference in data state

Status: Last call for comments

Attempt to consume a character reference, with no additional allowed character.

If nothing is returned, emit a U+0026 AMPERSAND character token.

Otherwise, emit the character token that was returned.

Finally, switch to the data state.

8.2.4.3 RCDATA state

Status: Last call for comments

Consume the next input character:

U+0026 AMPERSAND (&): Switch to the character reference in RCDATA state.
U+003C LESS-THAN SIGN (<): Switch to the RCDATA less-than sign state.
EOF: Emit an end-of-file token.
Anything else: Emit the current input character as a character token. Stay in the RCDATA state.

8.2.4.4 Character reference in RCDATA state

Attempt to consume a character reference, with no additional allowed character.

If nothing is returned, emit a U+0026 AMPERSAND character token.

Otherwise, emit the character token that was returned.

Finally, switch to the RCDATA state.

8.2.4.5 RAWTEXT state

Status: Last call for comments

Consume the next input character:

U+003C LESS-THAN SIGN (<): Switch to the RAWTEXT less-than sign state.
EOF: Emit an end-of-file token.
Anything else: Emit the current input character as a character token. Stay in the RAWTEXT state.

8.2.4.6 Script data state

Status: Last call for comments

Consume the next input character:

U+003C LESS-THAN SIGN (<): Switch to the script data less-than sign state.
EOF: Emit an end-of-file token.
Anything else: Emit the current input character as a character token. Stay in the script data state.

8.2.4.7 PLAINTEXT state

Status: Last call for comments

Consume the next input character:

EOF: Emit an end-of-file token.
Anything else: Emit the current input character as a character token. Stay in the PLAINTEXT state.

8.2.4.8 Tag open state

Status: Last call for comments

Consume the next input character:

U+0021 EXCLAMATION MARK (!): Switch to the markup declaration open state.
U+002F SOLIDUS (/): Switch to the end tag open state.
U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Create a new start tag token, set its tag name to the lowercase version of the current input character (add 0x0020 to the character's code point), then switch to the tag name state. (Don't emit the token yet; further details will be filled in before it is emitted.)
U+0061 LATIN SMALL LETTER A through to U+007A LATIN SMALL LETTER Z: Create a new start tag token, set its tag name to the current input character, then switch to the tag name state. (Don't emit the token yet; further details will be filled in before it is emitted.)
U+003F QUESTION MARK (?): Parse error. Switch to the bogus comment state.
Anything else: Parse error. Emit a U+003C LESS-THAN SIGN character token and reconsume the current input character in the data state.

8.2.4.9 End tag open state

Consume the next input character:

U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Create a new end tag token, set its tag name to the lowercase version of the current input character (add 0x0020 to the character's code point), then switch to the tag name state. (Don't emit the token yet; further details will be filled in before it is emitted.)
U+0061 LATIN SMALL LETTER A through to U+007A LATIN SMALL LETTER Z: Create a new end tag token, set its tag name to the current input character, then switch to the tag name state. (Don't emit the token yet; further details will be filled in before it is emitted.)
U+003E GREATER-THAN SIGN (>): Parse error. Switch to the data state.
EOF: Parse error. Emit a U+003C LESS-THAN SIGN character token and a U+002F SOLIDUS character token. Reconsume the EOF character in the data state.
Anything else: Parse error. Switch to the bogus comment state.

8.2.4.10 Tag name state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the before attribute name state.
U+002F SOLIDUS (/): Switch to the self-closing start tag state.
U+003E GREATER-THAN SIGN (>): Emit the current tag token. Switch to the data state.
U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Append the lowercase version of the current input character (add 0x0020 to the character's code point) to the current tag token's tag name. Stay in the tag name state.
EOF: Parse error. Reconsume the EOF character in the data state.
Anything else: Append the current input character to the current tag token's tag name. Stay in the tag name state.

8.2.4.11 RCDATA less-than sign state

Status: Last call for comments

Consume the next input character:

U+002F SOLIDUS (/): Set the temporary buffer to the empty string. Switch to the RCDATA end tag open state.
Anything else: Emit a U+003C LESS-THAN SIGN character token and reconsume the current input character in the RCDATA state.

8.2.4.12 RCDATA end tag open state

Status: Last call for comments

Consume the next input character:

U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Create a new end tag token, and set its tag name to the lowercase version of the current input character (add 0x0020 to the character's code point). Append the current input character to the temporary buffer. Finally, switch to the RCDATA end tag name state. (Don't emit the token yet; further details will be filled in before it is emitted.)
U+0061 LATIN SMALL LETTER A through to U+007A LATIN SMALL LETTER Z: Create a new end tag token, and set its tag name to the current input character. Append the current input character to the temporary buffer. Finally, switch to the RCDATA end tag name state. (Don't emit the token yet; further details will be filled in before it is emitted.)
Anything else: Emit a U+003C LESS-THAN SIGN character token, a U+002F SOLIDUS character token, and reconsume the current input character in the RCDATA state.

8.2.4.13 RCDATA end tag name state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: If the current end tag token is an appropriate end tag token, then switch to the before attribute name state. Otherwise, treat it as per the "anything else" entry below.
U+002F SOLIDUS (/): If the current end tag token is an appropriate end tag token, then switch to the self-closing start tag state. Otherwise, treat it as per the "anything else" entry below.
U+003E GREATER-THAN SIGN (>): If the current end tag token is an appropriate end tag token, then emit the current tag token and switch to the data state. Otherwise, treat it as per the "anything else" entry below.
U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Append the lowercase version of the current input character (add 0x0020 to the character's code point) to the current tag token's tag name. Append the current input character to the temporary buffer. Stay in the RCDATA end tag name state.
U+0061 LATIN SMALL LETTER A through to U+007A LATIN SMALL LETTER Z: Append the current input character to the current tag token's tag name. Append the current input character to the temporary buffer. Stay in the RCDATA end tag name state.
Anything else: Emit a U+003C LESS-THAN SIGN character token, a U+002F SOLIDUS character token, a character token for each of the characters in the temporary buffer (in the order they were added to the buffer), and reconsume the current input character in the RCDATA state.

8.2.4.14 RAWTEXT less-than sign state

Status: Last call for comments

Consume the next input character:

U+002F SOLIDUS (/): Set the temporary buffer to the empty string. Switch to the RAWTEXT end tag open state.
Anything else: Emit a U+003C LESS-THAN SIGN character token and reconsume the current input character in the RAWTEXT state.

8.2.4.15 RAWTEXT end tag open state

Status: Last call for comments

Consume the next input character:

U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Create a new end tag token, and set its tag name to the lowercase version of the current input character (add 0x0020 to the character's code point). Append the current input character to the temporary buffer. Finally, switch to the RAWTEXT end tag name state. (Don't emit the token yet; further details will be filled in before it is emitted.)
U+0061 LATIN SMALL LETTER A through to U+007A LATIN SMALL LETTER Z: Create a new end tag token, and set its tag name to the current input character. Append the current input character to the temporary buffer. Finally, switch to the RAWTEXT end tag name state. (Don't emit the token yet; further details will be filled in before it is emitted.)
Anything else: Emit a U+003C LESS-THAN SIGN character token, a U+002F SOLIDUS character token, and reconsume the current input character in the RAWTEXT state.

8.2.4.16 RAWTEXT end tag name state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: If the current end tag token is an appropriate end tag token, then switch to the before attribute name state. Otherwise, treat it as per the "anything else" entry below.
U+002F SOLIDUS (/): If the current end tag token is an appropriate end tag token, then switch to the self-closing start tag state. Otherwise, treat it as per the "anything else" entry below.
U+003E GREATER-THAN SIGN (>): If the current end tag token is an appropriate end tag token, then emit the current tag token and switch to the data state. Otherwise, treat it as per the "anything else" entry below.
U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Append the lowercase version of the current input character (add 0x0020 to the character's code point) to the current tag token's tag name. Append the current input character to the temporary buffer. Stay in the RAWTEXT end tag name state.
U+0061 LATIN SMALL LETTER A through to U+007A LATIN SMALL LETTER Z: Append the current input character to the current tag token's tag name. Append the current input character to the temporary buffer. Stay in the RAWTEXT end tag name state.
Anything else: Emit a U+003C LESS-THAN SIGN character token, a U+002F SOLIDUS character token, a character token for each of the characters in the temporary buffer (in the order they were added to the buffer), and reconsume the current input character in the RAWTEXT state.

8.2.4.17 Script data less-than sign state

Status: Last call for comments

Consume the next input character:

U+002F SOLIDUS (/): Set the temporary buffer to the empty string. Switch to the script data end tag open state.
U+0021 EXCLAMATION MARK (!): Emit a U+003C LESS-THAN SIGN character token and a U+0021 EXCLAMATION MARK character token. Switch to the script data escape start state.
Anything else: Emit a U+003C LESS-THAN SIGN character token and reconsume the current input character in the script data state.

8.2.4.18 Script data end tag open state

Status: Last call for comments

Consume the next input character:

U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Create a new end tag token, and set its tag name to the lowercase version of the current input character (add 0x0020 to the character's code point). Append the current input character to the temporary buffer. Finally, switch to the script data end tag name state. (Don't emit the token yet; further details will be filled in before it is emitted.)
U+0061 LATIN SMALL LETTER A through to U+007A LATIN SMALL LETTER Z: Create a new end tag token, and set its tag name to the current input character. Append the current input character to the temporary buffer. Finally, switch to the script data end tag name state. (Don't emit the token yet; further details will be filled in before it is emitted.)
Anything else: Emit a U+003C LESS-THAN SIGN character token, a U+002F SOLIDUS character token, and reconsume the current input character in the script data state.

8.2.4.19 Script data end tag name state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: If the current end tag token is an appropriate end tag token, then switch to the before attribute name state. Otherwise, treat it as per the "anything else" entry below.
U+002F SOLIDUS (/): If the current end tag token is an appropriate end tag token, then switch to the self-closing start tag state. Otherwise, treat it as per the "anything else" entry below.
U+003E GREATER-THAN SIGN (>): If the current end tag token is an appropriate end tag token, then emit the current tag token and switch to the data state. Otherwise, treat it as per the "anything else" entry below.
U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Append the lowercase version of the current input character (add 0x0020 to the character's code point) to the current tag token's tag name. Append the current input character to the temporary buffer. Stay in the script data end tag name state.
U+0061 LATIN SMALL LETTER A through to U+007A LATIN SMALL LETTER Z: Append the current input character to the current tag token's tag name. Append the current input character to the temporary buffer. Stay in the script data end tag name state.
Anything else: Emit a U+003C LESS-THAN SIGN character token, a U+002F SOLIDUS character token, a character token for each of the characters in the temporary buffer (in the order they were added to the buffer), and reconsume the current input character in the script data state.

8.2.4.20 Script data escape start state

Status: Last call for comments

Consume the next input character:

U+002D HYPHEN-MINUS (-): Emit a U+002D HYPHEN-MINUS character token. Switch to the script data escape start dash state.
Anything else: Reconsume the current input character in the script data state.

8.2.4.21 Script data escape start dash state

Status: Last call for comments

Consume the next input character:

U+002D HYPHEN-MINUS (-): Emit a U+002D HYPHEN-MINUS character token. Switch to the script data escaped dash dash state.
Anything else: Reconsume the current input character in the script data state.

8.2.4.22 Script data escaped state

Status: Last call for comments

Consume the next input character:

U+002D HYPHEN-MINUS (-): Emit a U+002D HYPHEN-MINUS character token. Switch to the script data escaped dash state.
U+003C LESS-THAN SIGN (<): Switch to the script data escaped less-than sign state.
EOF: Parse error. Reconsume the EOF character in the data state.
Anything else: Emit the current input character as a character token. Stay in the script data escaped state.

8.2.4.23 Script data escaped dash state

Status: Last call for comments

Consume the next input character:

U+002D HYPHEN-MINUS (-): Emit a U+002D HYPHEN-MINUS character token. Switch to the script data escaped dash dash state.
U+003C LESS-THAN SIGN (<): Switch to the script data escaped less-than sign state.
EOF: Parse error. Reconsume the EOF character in the data state.
Anything else: Emit the current input character as a character token. Switch to the script data escaped state.

8.2.4.24 Script data escaped dash dash state

Status: Last call for comments

Consume the next input character:

U+002D HYPHEN-MINUS (-): Emit a U+002D HYPHEN-MINUS character token. Stay in the script data escaped dash dash state.
U+003C LESS-THAN SIGN (<): Switch to the script data escaped less-than sign state.
U+003E GREATER-THAN SIGN (>): Emit a U+003E GREATER-THAN SIGN character token. Switch to the script data state.
EOF: Parse error. Reconsume the EOF character in the data state.
Anything else: Emit the current input character as a character token. Switch to the script data escaped state.

8.2.4.25 Script data escaped less-than sign state

Status: Last call for comments

Consume the next input character:

U+002F SOLIDUS (/): Set the temporary buffer to the empty string. Switch to the script data escaped end tag open state.
U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Emit a U+003C LESS-THAN SIGN character token and the current input character as a character token. Set the temporary buffer to the empty string. Append the lowercase version of the current input character (add 0x0020 to the character's code point) to the temporary buffer. Switch to the script data double escape start state.
U+0061 LATIN SMALL LETTER A through to U+007A LATIN SMALL LETTER Z: Emit a U+003C LESS-THAN SIGN character token and the current input character as a character token. Set the temporary buffer to the empty string. Append the current input character to the temporary buffer. Switch to the script data double escape start state.
Anything else: Emit a U+003C LESS-THAN SIGN character token and reconsume the current input character in the script data escaped state.

8.2.4.26 Script data escaped end tag open state

Status: Last call for comments

Consume the next input character:

U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Create a new end tag token, and set its tag name to the lowercase version of the current input character (add 0x0020 to the character's code point). Append the current input character to the temporary buffer. Finally, switch to the script data escaped end tag name state. (Don't emit the token yet; further details will be filled in before it is emitted.)
U+0061 LATIN SMALL LETTER A through to U+007A LATIN SMALL LETTER Z: Create a new end tag token, and set its tag name to the current input character. Append the current input character to the temporary buffer. Finally, switch to the script data escaped end tag name state. (Don't emit the token yet; further details will be filled in before it is emitted.)
Anything else: Emit a U+003C LESS-THAN SIGN character token, a U+002F SOLIDUS character token, and reconsume the current input character in the script data escaped state.

8.2.4.27 Script data escaped end tag name state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: If the current end tag token is an appropriate end tag token, then switch to the before attribute name state. Otherwise, treat it as per the "anything else" entry below.
U+002F SOLIDUS (/): If the current end tag token is an appropriate end tag token, then switch to the self-closing start tag state. Otherwise, treat it as per the "anything else" entry below.
U+003E GREATER-THAN SIGN (>): If the current end tag token is an appropriate end tag token, then emit the current tag token and switch to the data state. Otherwise, treat it as per the "anything else" entry below.
U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Append the lowercase version of the current input character (add 0x0020 to the character's code point) to the current tag token's tag name. Append the current input character to the temporary buffer. Stay in the script data escaped end tag name state.
U+0061 LATIN SMALL LETTER A through to U+007A LATIN SMALL LETTER Z: Append the current input character to the current tag token's tag name. Append the current input character to the temporary buffer. Stay in the script data escaped end tag name state.
Anything else: Emit a U+003C LESS-THAN SIGN character token, a U+002F SOLIDUS character token, a character token for each of the characters in the temporary buffer (in the order they were added to the buffer), and reconsume the current input character in the script data escaped state.

8.2.4.28 Script data double escape start state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE
U+002F SOLIDUS (/)
U+003E GREATER-THAN SIGN (>): Emit the current input character as a character token. If the temporary buffer is the string "script", then switch to the script data double escaped state. Otherwise, switch to the script data escaped state.
U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Emit the current input character as a character token. Append the lowercase version of the current input character (add 0x0020 to the character's code point) to the temporary buffer. Stay in the script data double escape start state.
U+0061 LATIN SMALL LETTER A through to U+007A LATIN SMALL LETTER Z: Emit the current input character as a character token. Append the current input character to the temporary buffer. Stay in the script data double escape start state.
Anything else: Reconsume the current input character in the script data escaped state.

8.2.4.29 Script data double escaped state

Status: Last call for comments

Consume the next input character:

U+002D HYPHEN-MINUS (-): Emit a U+002D HYPHEN-MINUS character token. Switch to the script data double escaped dash state.
U+003C LESS-THAN SIGN (<): Emit a U+003C LESS-THAN SIGN character token. Switch to the script data double escaped less-than sign state.
EOF: Parse error. Reconsume the EOF character in the data state.
Anything else: Emit the current input character as a character token. Stay in the script data double escaped state.

8.2.4.30 Script data double escaped dash state

Status: Last call for comments

Consume the next input character:

U+002D HYPHEN-MINUS (-): Emit a U+002D HYPHEN-MINUS character token. Switch to the script data double escaped dash dash state.
U+003C LESS-THAN SIGN (<): Emit a U+003C LESS-THAN SIGN character token. Switch to the script data double escaped less-than sign state.
EOF: Parse error. Reconsume the EOF character in the data state.
Anything else: Emit the current input character as a character token. Switch to the script data double escaped state.

8.2.4.31 Script data double escaped dash dash state

Status: Last call for comments

Consume the next input character:

U+002D HYPHEN-MINUS (-): Emit a U+002D HYPHEN-MINUS character token. Stay in the script data double escaped dash dash state.
U+003C LESS-THAN SIGN (<): Emit a U+003C LESS-THAN SIGN character token. Switch to the script data double escaped less-than sign state.
U+003E GREATER-THAN SIGN (>): Emit a U+003E GREATER-THAN SIGN character token. Switch to the script data state.
EOF: Parse error. Reconsume the EOF character in the data state.
Anything else: Emit the current input character as a character token. Switch to the script data double escaped state.

8.2.4.32 Script data double escaped less-than sign state

Status: Last call for comments

Consume the next input character:

U+002F SOLIDUS (/): Emit a U+002F SOLIDUS character token. Set the temporary buffer to the empty string. Switch to the script data double escape end state.
Anything else: Reconsume the current input character in the script data double escaped state.

8.2.4.33 Script data double escape end state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE
U+002F SOLIDUS (/)
U+003E GREATER-THAN SIGN (>): Emit the current input character as a character token. If the temporary buffer is the string "script", then switch to the script data escaped state. Otherwise, switch to the script data double escaped state.
U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Emit the current input character as a character token. Append the lowercase version of the current input character (add 0x0020 to the character's code point) to the temporary buffer. Stay in the script data double escape end state.
U+0061 LATIN SMALL LETTER A through to U+007A LATIN SMALL LETTER Z: Emit the current input character as a character token. Append the current input character to the temporary buffer. Stay in the script data double escape end state.
Anything else: Reconsume the current input character in the script data double escaped state.

8.2.4.34 Before attribute name state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Stay in the before attribute name state.
U+002F SOLIDUS (/): Switch to the self-closing start tag state.
U+003E GREATER-THAN SIGN (>): Emit the current tag token. Switch to the data state.
U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Start a new attribute in the current tag token. Set that attribute's name to the lowercase version of the current input character (add 0x0020 to the character's code point), and its value to the empty string. Switch to the attribute name state.
U+0022 QUOTATION MARK (")
U+0027 APOSTROPHE (')
U+003C LESS-THAN SIGN (<)
U+003D EQUALS SIGN (=): Parse error. Treat it as per the "anything else" entry below.
EOF: Parse error. Reconsume the EOF character in the data state.
Anything else: Start a new attribute in the current tag token. Set that attribute's name to the current input character, and its value to the empty string. Switch to the attribute name state.

8.2.4.35 Attribute name state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the after attribute name state.
U+002F SOLIDUS (/): Switch to the self-closing start tag state.
U+003D EQUALS SIGN (=): Switch to the before attribute value state.
U+003E GREATER-THAN SIGN (>): Emit the current tag token. Switch to the data state.
U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Append the lowercase version of the current input character (add 0x0020 to the character's code point) to the current attribute's name. Stay in the attribute name state.
U+0022 QUOTATION MARK (")
U+0027 APOSTROPHE (')
U+003C LESS-THAN SIGN (<): Parse error. Treat it as per the "anything else" entry below.
EOF: Parse error. Reconsume the EOF character in the data state.
Anything else: Append the current input character to the current attribute's name. Stay in the attribute name state.

When the user agent leaves the attribute name state (and before emitting the tag token, if appropriate), the complete attribute's name must be compared to the other attributes on the same token; if there is already an attribute on the token with the exact same name, then this is a parse error and the new attribute must be dropped, along with the value that gets associated with it (if any).

8.2.4.36 After attribute name state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Stay in the after attribute name state.
U+002F SOLIDUS (/): Switch to the self-closing start tag state.
U+003D EQUALS SIGN (=): Switch to the before attribute value state.
U+003E GREATER-THAN SIGN (>): Emit the current tag token. Switch to the data state.
U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Start a new attribute in the current tag token. Set that attribute's name to the lowercase version of the current input character (add 0x0020 to the character's code point), and its value to the empty string. Switch to the attribute name state.
U+0022 QUOTATION MARK (")
U+0027 APOSTROPHE (')
U+003C LESS-THAN SIGN (<): Parse error. Treat it as per the "anything else" entry below.
EOF: Parse error. Reconsume the EOF character in the data state.
Anything else: Start a new attribute in the current tag token. Set that attribute's name to the current input character, and its value to the empty string. Switch to the attribute name state.

8.2.4.37 Before attribute value state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Stay in the before attribute value state.
U+0022 QUOTATION MARK ("): Switch to the attribute value (double-quoted) state.
U+0026 AMPERSAND (&): Switch to the attribute value (unquoted) state and reconsume this current input character.
U+0027 APOSTROPHE ('): Switch to the attribute value (single-quoted) state.
U+003E GREATER-THAN SIGN (>): Parse error. Emit the current tag token. Switch to the data state.
U+003C LESS-THAN SIGN (<)
U+003D EQUALS SIGN (=)
U+0060 GRAVE ACCENT (`): Parse error. Treat it as per the "anything else" entry below.
EOF: Parse error. Reconsume the EOF character in the data state.
Anything else: Append the current input character to the current attribute's value. Switch to the attribute value (unquoted) state.

8.2.4.38 Attribute value (double-quoted) state

Consume the next input character:

U+0022 QUOTATION MARK ("): Switch to the after attribute value (quoted) state.
U+0026 AMPERSAND (&): Switch to the character reference in attribute value state, with the additional allowed character being U+0022 QUOTATION MARK (").
EOF: Parse error. Reconsume the EOF character in the data state.
Anything else: Append the current input character to the current attribute's value. Stay in the attribute value (double-quoted) state.

8.2.4.39 Attribute value (single-quoted) state

Consume the next input character:

U+0027 APOSTROPHE ('): Switch to the after attribute value (quoted) state.
U+0026 AMPERSAND (&): Switch to the character reference in attribute value state, with the additional allowed character being U+0027 APOSTROPHE (').
EOF: Parse error. Reconsume the EOF character in the data state.
Anything else: Append the current input character to the current attribute's value. Stay in the attribute value (single-quoted) state.

8.2.4.40 Attribute value (unquoted) state

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the before attribute name state.
U+0026 AMPERSAND (&): Switch to the character reference in attribute value state, with the additional allowed character being U+003E GREATER-THAN SIGN (>).
U+003E GREATER-THAN SIGN (>): Emit the current tag token. Switch to the data state.
U+0022 QUOTATION MARK (")
U+0027 APOSTROPHE (')
U+003C LESS-THAN SIGN (<)
U+003D EQUALS SIGN (=)
U+0060 GRAVE ACCENT (`): Parse error. Treat it as per the "anything else" entry below.
EOF: Parse error. Reconsume the EOF character in the data state.
Anything else: Append the current input character to the current attribute's value. Stay in the attribute value (unquoted) state.

8.2.4.41 Character reference in attribute value state

Status: Last call for comments

Attempt to consume a character reference.

If nothing is returned, append a U+0026 AMPERSAND character to the current attribute's value.

Otherwise, append the returned character token to the current attribute's value.

Finally, switch back to the attribute value state that you were in when were switched into this state.

8.2.4.42 After attribute value (quoted) state

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the before attribute name state.
U+002F SOLIDUS (/): Switch to the self-closing start tag state.
U+003E GREATER-THAN SIGN (>): Emit the current tag token. Switch to the data state.
EOF: Parse error. Reconsume the EOF character in the data state.
Anything else: Parse error. Reconsume the character in the before attribute name state.

8.2.4.43 Self-closing start tag state

Status: Last call for comments

Consume the next input character:

U+003E GREATER-THAN SIGN (>): Set the self-closing flag of the current tag token. Emit the current tag token. Switch to the data state.
EOF: Parse error. Reconsume the EOF character in the data state.
Anything else: Parse error. Reconsume the character in the before attribute name state.

8.2.4.44 Bogus comment state

Status: Last call for comments

Consume every character up to and including the first U+003E GREATER-THAN SIGN character (>) or the end of the file (EOF), whichever comes first. Emit a comment token whose data is the concatenation of all the characters starting from and including the character that caused the state machine to switch into the bogus comment state, up to and including the character immediately before the last consumed character (i.e. up to the character just before the U+003E or EOF character). (If the comment was started by the end of the file (EOF), the token is empty.)

Switch to the data state.

If the end of the file was reached, reconsume the EOF character.

8.2.4.45 Markup declaration open state

Status: Last call for comments

If the next two characters are both U+002D HYPHEN-MINUS characters (-), consume those two characters, create a comment token whose data is the empty string, and switch to the comment start state.

Otherwise, if the next seven characters are an ASCII case-insensitive match for the word "DOCTYPE", then consume those characters and switch to the DOCTYPE state.

Otherwise, if the insertion mode is "in foreign content" and the current node is not an element in the HTML namespace and the next seven characters are an case-sensitive match for the string "[CDATA[" (the five uppercase letters "CDATA" with a U+005B LEFT SQUARE BRACKET character before and after), then consume those characters and switch to the CDATA section state.

Otherwise, this is a parse error. Switch to the bogus comment state. The next character that is consumed, if any, is the first character that will be in the comment.

8.2.4.46 Comment start state

Status: Last call for comments

Consume the next input character:

U+002D HYPHEN-MINUS (-): Switch to the comment start dash state.
U+003E GREATER-THAN SIGN (>): Parse error. Emit the comment token. Switch to the data state.
EOF: Parse error. Emit the comment token. Reconsume the EOF character in the data state.
Anything else: Append the current input character to the comment token's data. Switch to the comment state.

8.2.4.47 Comment start dash state

Status: Last call for comments

Consume the next input character:

U+002D HYPHEN-MINUS (-): Switch to the comment end state
U+003E GREATER-THAN SIGN (>): Parse error. Emit the comment token. Switch to the data state.
EOF: Parse error. Emit the comment token. Reconsume the EOF character in the data state.
Anything else: Append a U+002D HYPHEN-MINUS character (-) and the current input character to the comment token's data. Switch to the comment state.

8.2.4.48 Comment state

Status: Last call for comments

Consume the next input character:

U+002D HYPHEN-MINUS (-): Switch to the comment end dash state
EOF: Parse error. Emit the comment token. Reconsume the EOF character in the data state.
Anything else: Append the current input character to the comment token's data. Stay in the comment state.

8.2.4.49 Comment end dash state

Status: Last call for comments

Consume the next input character:

U+002D HYPHEN-MINUS (-): Switch to the comment end state
EOF: Parse error. Emit the comment token. Reconsume the EOF character in the data state.
Anything else: Append a U+002D HYPHEN-MINUS character (-) and the current input character to the comment token's data. Switch to the comment state.

8.2.4.50 Comment end state

Status: Last call for comments

Consume the next input character:

U+003E GREATER-THAN SIGN (>): Emit the comment token. Switch to the data state.
U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Parse error. Append two U+002D HYPHEN-MINUS characters (-) and the current input character to the comment token's data. Switch to the comment end space state.
U+0021 EXCLAMATION MARK (!): Parse error. Switch to the comment end bang state.
U+002D HYPHEN-MINUS (-): Parse error. Append a U+002D HYPHEN-MINUS character (-) to the comment token's data. Stay in the comment end state.
EOF: Parse error. Emit the comment token. Reconsume the EOF character in the data state.
Anything else: Parse error. Append two U+002D HYPHEN-MINUS characters (-) and the current input character to the comment token's data. Switch to the comment state.

8.2.4.51 Comment end bang state

Status: Last call for comments

Consume the next input character:

U+002D HYPHEN-MINUS (-): Append two U+002D HYPHEN-MINUS characters (-) and a U+0021 EXCLAMATION MARK character (!) to the comment token's data. Switch to the comment end dash state.
U+003E GREATER-THAN SIGN (>): Emit the comment token. Switch to the data state.
EOF: Parse error. Emit the comment token. Reconsume the EOF character in the data state.
Anything else: Append two U+002D HYPHEN-MINUS characters (-), a U+0021 EXCLAMATION MARK character (!), and the current input character to the comment token's data. Switch to the comment state.

8.2.4.52 Comment end space state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Append the current input character to the comment token's data. Stay in the comment end space state.
U+002D HYPHEN-MINUS (-): Switch to the comment end dash state.
U+003E GREATER-THAN SIGN (>): Emit the comment token. Switch to the data state.
EOF: Parse error. Emit the comment token. Reconsume the EOF character in the data state.
Anything else: Append the current input character to the comment token's data. Switch to the comment state.

8.2.4.53 DOCTYPE state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the before DOCTYPE name state.
EOF: Parse error. Create a new DOCTYPE token. Set its force-quirks flag to on. Emit the token. Reconsume the EOF character in the data state.
Anything else: Parse error. Reconsume the character in the before DOCTYPE name state.

8.2.4.54 Before DOCTYPE name state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Stay in the before DOCTYPE name state.
U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Create a new DOCTYPE token. Set the token's name to the lowercase version of the current input character (add 0x0020 to the character's code point). Switch to the DOCTYPE name state.
U+003E GREATER-THAN SIGN (>): Parse error. Create a new DOCTYPE token. Set its force-quirks flag to on. Emit the token. Switch to the data state.
EOF: Parse error. Create a new DOCTYPE token. Set its force-quirks flag to on. Emit the token. Reconsume the EOF character in the data state.
Anything else: Create a new DOCTYPE token. Set the token's name to the current input character. Switch to the DOCTYPE name state.

8.2.4.55 DOCTYPE name state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the after DOCTYPE name state.
U+003E GREATER-THAN SIGN (>): Emit the current DOCTYPE token. Switch to the data state.
U+0041 LATIN CAPITAL LETTER A through to U+005A LATIN CAPITAL LETTER Z: Append the lowercase version of the current input character (add 0x0020 to the character's code point) to the current DOCTYPE token's name. Stay in the DOCTYPE name state.
EOF: Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Reconsume the EOF character in the data state.
Anything else: Append the current input character to the current DOCTYPE token's name. Stay in the DOCTYPE name state.

8.2.4.56 After DOCTYPE name state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION

U+000A LINE FEED (LF)

U+000C FORM FEED (FF)

U+0020 SPACE

Stay in the after DOCTYPE name state.

U+003E GREATER-THAN SIGN (>)

Emit the current DOCTYPE token. Switch to the data state.

EOF

Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Reconsume the EOF character in the data state.

Anything else

If the six characters starting from the current input character are an ASCII case-insensitive match for the word "PUBLIC", then consume those characters and switch to the after DOCTYPE public keyword state.

Otherwise, if the six characters starting from the current input character are an ASCII case-insensitive match for the word "SYSTEM", then consume those characters and switch to the after DOCTYPE system keyword state.

Otherwise, this is the parse error. Set the DOCTYPE token's force-quirks flag to on. Switch to the bogus DOCTYPE state.

8.2.4.57 After DOCTYPE public keyword state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the before DOCTYPE public identifier state.
U+0022 QUOTATION MARK ("): Parse error. Set the DOCTYPE token's public identifier to the empty string (not missing), then switch to the DOCTYPE public identifier (double-quoted) state.
U+0027 APOSTROPHE ('): Parse error. Set the DOCTYPE token's public identifier to the empty string (not missing), then switch to the DOCTYPE public identifier (single-quoted) state.
U+003E GREATER-THAN SIGN (>): Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Switch to the data state.
EOF: Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Reconsume the EOF character in the data state.
Anything else: Parse error. Set the DOCTYPE token's force-quirks flag to on. Switch to the bogus DOCTYPE state.

8.2.4.58 Before DOCTYPE public identifier state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Stay in the before DOCTYPE public identifier state.
U+0022 QUOTATION MARK ("): Set the DOCTYPE token's public identifier to the empty string (not missing), then switch to the DOCTYPE public identifier (double-quoted) state.
U+0027 APOSTROPHE ('): Set the DOCTYPE token's public identifier to the empty string (not missing), then switch to the DOCTYPE public identifier (single-quoted) state.
U+003E GREATER-THAN SIGN (>): Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Switch to the data state.
EOF: Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Reconsume the EOF character in the data state.
Anything else: Parse error. Set the DOCTYPE token's force-quirks flag to on. Switch to the bogus DOCTYPE state.

8.2.4.59 DOCTYPE public identifier (double-quoted) state

Consume the next input character:

U+0022 QUOTATION MARK ("): Switch to the after DOCTYPE public identifier state.
U+003E GREATER-THAN SIGN (>): Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Switch to the data state.
EOF: Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Reconsume the EOF character in the data state.
Anything else: Append the current input character to the current DOCTYPE token's public identifier. Stay in the DOCTYPE public identifier (double-quoted) state.

8.2.4.60 DOCTYPE public identifier (single-quoted) state

Consume the next input character:

U+0027 APOSTROPHE ('): Switch to the after DOCTYPE public identifier state.
U+003E GREATER-THAN SIGN (>): Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Switch to the data state.
EOF: Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Reconsume the EOF character in the data state.
Anything else: Append the current input character to the current DOCTYPE token's public identifier. Stay in the DOCTYPE public identifier (single-quoted) state.

8.2.4.61 After DOCTYPE public identifier state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the between DOCTYPE public and system identifiers state.
U+003E GREATER-THAN SIGN (>): Emit the current DOCTYPE token. Switch to the data state.
U+0022 QUOTATION MARK ("): Parse error. Set the DOCTYPE token's system identifier to the empty string (not missing), then switch to the DOCTYPE system identifier (double-quoted) state.
U+0027 APOSTROPHE ('): Parse error. Set the DOCTYPE token's system identifier to the empty string (not missing), then switch to the DOCTYPE system identifier (single-quoted) state.
EOF: Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Reconsume the EOF character in the data state.
Anything else: Parse error. Set the DOCTYPE token's force-quirks flag to on. Switch to the bogus DOCTYPE state.

8.2.4.62 Between DOCTYPE public and system identifiers state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Stay in the between DOCTYPE public and system identifiers state.
U+003E GREATER-THAN SIGN (>): Emit the current DOCTYPE token. Switch to the data state.
U+0022 QUOTATION MARK ("): Set the DOCTYPE token's system identifier to the empty string (not missing), then switch to the DOCTYPE system identifier (double-quoted) state.
U+0027 APOSTROPHE ('): Set the DOCTYPE token's system identifier to the empty string (not missing), then switch to the DOCTYPE system identifier (single-quoted) state.
EOF: Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Reconsume the EOF character in the data state.
Anything else: Parse error. Set the DOCTYPE token's force-quirks flag to on. Switch to the bogus DOCTYPE state.

8.2.4.63 After DOCTYPE system keyword state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Switch to the before DOCTYPE system identifier state.
U+0022 QUOTATION MARK ("): Parse error. Set the DOCTYPE token's system identifier to the empty string (not missing), then switch to the DOCTYPE system identifier (double-quoted) state.
U+0027 APOSTROPHE ('): Parse error. Set the DOCTYPE token's system identifier to the empty string (not missing), then switch to the DOCTYPE system identifier (single-quoted) state.
U+003E GREATER-THAN SIGN (>): Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Switch to the data state.
EOF: Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Reconsume the EOF character in the data state.
Anything else: Parse error. Set the DOCTYPE token's force-quirks flag to on. Switch to the bogus DOCTYPE state.

8.2.4.64 Before DOCTYPE system identifier state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Stay in the before DOCTYPE system identifier state.
U+0022 QUOTATION MARK ("): Set the DOCTYPE token's system identifier to the empty string (not missing), then switch to the DOCTYPE system identifier (double-quoted) state.
U+0027 APOSTROPHE ('): Set the DOCTYPE token's system identifier to the empty string (not missing), then switch to the DOCTYPE system identifier (single-quoted) state.
U+003E GREATER-THAN SIGN (>): Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Switch to the data state.
EOF: Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Reconsume the EOF character in the data state.
Anything else: Parse error. Set the DOCTYPE token's force-quirks flag to on. Switch to the bogus DOCTYPE state.

8.2.4.65 DOCTYPE system identifier (double-quoted) state

Consume the next input character:

U+0022 QUOTATION MARK ("): Switch to the after DOCTYPE system identifier state.
U+003E GREATER-THAN SIGN (>): Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Switch to the data state.
EOF: Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Reconsume the EOF character in the data state.
Anything else: Append the current input character to the current DOCTYPE token's system identifier. Stay in the DOCTYPE system identifier (double-quoted) state.

8.2.4.66 DOCTYPE system identifier (single-quoted) state

Consume the next input character:

U+0027 APOSTROPHE ('): Switch to the after DOCTYPE system identifier state.
U+003E GREATER-THAN SIGN (>): Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Switch to the data state.
EOF: Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Reconsume the EOF character in the data state.
Anything else: Append the current input character to the current DOCTYPE token's system identifier. Stay in the DOCTYPE system identifier (single-quoted) state.

8.2.4.67 After DOCTYPE system identifier state

Status: Last call for comments

Consume the next input character:

U+0009 CHARACTER TABULATION
U+000A LINE FEED (LF)
U+000C FORM FEED (FF)
U+0020 SPACE: Stay in the after DOCTYPE system identifier state.
U+003E GREATER-THAN SIGN (>): Emit the current DOCTYPE token. Switch to the data state.
EOF: Parse error. Set the DOCTYPE token's force-quirks flag to on. Emit that DOCTYPE token. Reconsume the EOF character in the data state.
Anything else: Parse error. Switch to the bogus DOCTYPE state. (This does not set the DOCTYPE token's force-quirks flag to on.)

8.2.4.68 Bogus DOCTYPE state

Status: Last call for comments

Consume the next input character:

U+003E GREATER-THAN SIGN (>): Emit the DOCTYPE token. Switch to the data state.
EOF: Emit the DOCTYPE token. Reconsume the EOF character in the data state.
Anything else: Stay in the bogus DOCTYPE state.

8.2.4.69 CDATA section state

Status: Last call for comments

Consume every character up to the next occurrence of the three character sequence U+005D RIGHT SQUARE BRACKET U+005D RIGHT SQUARE BRACKET U+003E GREATER-THAN SIGN (]]>), or the end of the file (EOF), whichever comes first. Emit a series of character tokens consisting of all the characters consumed except the matching three character sequence at the end (if one was found before the end of the file).

Switch to the data state.

If the end of the file was reached, reconsume the EOF character.

8.2.4.70 Tokenizing character references

Status: Last call for comments

This section defines how to consume a character reference. This definition is used when parsing character references in text and in attributes.

The behavior depends on the identity of the next character (the one immediately after the U+0026 AMPERSAND character):

U+0009 CHARACTER TABULATION

U+000A LINE FEED (LF)

U+000C FORM FEED (FF)

U+0020 SPACE

U+003C LESS-THAN SIGN

U+0026 AMPERSAND

EOF

The additional allowed character, if there is one

Not a character reference. No characters are consumed, and nothing is returned. (This is not an error, either.)

U+0023 NUMBER SIGN (#)

Consume the U+0023 NUMBER SIGN.

The behavior further depends on the character after the U+0023 NUMBER SIGN:

U+0078 LATIN SMALL LETTER X

U+0058 LATIN CAPITAL LETTER X

Consume the X.

Follow the steps below, but using the range of characters U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), U+0061 LATIN SMALL LETTER A to U+0066 LATIN SMALL LETTER F, and U+0041 LATIN CAPITAL LETTER A to U+0046 LATIN CAPITAL LETTER F (in other words, 0-9, A-F, a-f).

When it comes to interpreting the number, interpret it as a hexadecimal number.

Anything else

Follow the steps below, but using the range of characters U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9).

When it comes to interpreting the number, interpret it as a decimal number.

Consume as many characters as match the range of characters given above.

If no characters match the range, then don't consume any characters (and unconsume the U+0023 NUMBER SIGN character and, if appropriate, the X character). This is a parse error; nothing is returned.

Otherwise, if the next character is a U+003B SEMICOLON, consume that too. If it isn't, there is a parse error.

If one or more characters match the range, then take them all and interpret the string of characters as a number (either hexadecimal or decimal as appropriate).

If that number is one of the numbers in the first column of the following table, then this is a parse error. Find the row with that number in the first column, and return a character token for the Unicode character given in the second column of that row.

Number	Unicode character
0x00	U+FFFD	REPLACEMENT CHARACTER
0x0D	U+000A	LINE FEED (LF)
0x80	U+20AC	EURO SIGN (€)
0x81	U+0081	<control>
0x82	U+201A	SINGLE LOW-9 QUOTATION MARK (‚)
0x83	U+0192	LATIN SMALL LETTER F WITH HOOK (ƒ)
0x84	U+201E	DOUBLE LOW-9 QUOTATION MARK („)
0x85	U+2026	HORIZONTAL ELLIPSIS (…)
0x86	U+2020	DAGGER (†)
0x87	U+2021	DOUBLE DAGGER (‡)
0x88	U+02C6	MODIFIER LETTER CIRCUMFLEX ACCENT (ˆ)
0x89	U+2030	PER MILLE SIGN (‰)
0x8A	U+0160	LATIN CAPITAL LETTER S WITH CARON (Š)
0x8B	U+2039	SINGLE LEFT-POINTING ANGLE QUOTATION MARK (‹)
0x8C	U+0152	LATIN CAPITAL LIGATURE OE (Œ)
0x8D	U+008D	<control>
0x8E	U+017D	LATIN CAPITAL LETTER Z WITH CARON (Ž)
0x8F	U+008F	<control>
0x90	U+0090	<control>
0x91	U+2018	LEFT SINGLE QUOTATION MARK (‘)
0x92	U+2019	RIGHT SINGLE QUOTATION MARK (’)
0x93	U+201C	LEFT DOUBLE QUOTATION MARK (“)
0x94	U+201D	RIGHT DOUBLE QUOTATION MARK (”)
0x95	U+2022	BULLET (•)
0x96	U+2013	EN DASH (–)
0x97	U+2014	EM DASH (—)
0x98	U+02DC	SMALL TILDE (˜)
0x99	U+2122	TRADE MARK SIGN (™)
0x9A	U+0161	LATIN SMALL LETTER S WITH CARON (š)
0x9B	U+203A	SINGLE RIGHT-POINTING ANGLE QUOTATION MARK (›)
0x9C	U+0153	LATIN SMALL LIGATURE OE (œ)
0x9D	U+009D	<control>
0x9E	U+017E	LATIN SMALL LETTER Z WITH CARON (ž)
0x9F	U+0178	LATIN CAPITAL LETTER Y WITH DIAERESIS (Ÿ)

Otherwise, if the number is in the range 0xD800 to 0xDFFF or is greater than 0x10FFFF, then this is a parse error. Return a U+FFFD REPLACEMENT CHARACTER.

Otherwise, return a character token for the Unicode character whose code point is that number. If the number is in the range 0x0001 to 0x0008, 0x000E to 0x001F, 0x007F to 0x009F, 0xFDD0 to 0xFDEF, or is one of 0x000B, 0xFFFE, 0xFFFF, 0x1FFFE, 0x1FFFF, 0x2FFFE, 0x2FFFF, 0x3FFFE, 0x3FFFF, 0x4FFFE, 0x4FFFF, 0x5FFFE, 0x5FFFF, 0x6FFFE, 0x6FFFF, 0x7FFFE, 0x7FFFF, 0x8FFFE, 0x8FFFF, 0x9FFFE, 0x9FFFF, 0xAFFFE, 0xAFFFF, 0xBFFFE, 0xBFFFF, 0xCFFFE, 0xCFFFF, 0xDFFFE, 0xDFFFF, 0xEFFFE, 0xEFFFF, 0xFFFFE, 0xFFFFF, 0x10FFFE, or 0x10FFFF, then this is a parse error.

Anything else

Consume the maximum number of characters possible, with the consumed characters matching one of the identifiers in the first column of the named character references table (in a case-sensitive manner).

If no match can be made, then this is a parse error. No characters are consumed, and nothing is returned.

If the last character matched is not a U+003B SEMICOLON character (;), there is a parse error.

If the character reference is being consumed as part of an attribute, and the last character matched is not a U+003B SEMICOLON character (;), and the next character is in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), U+0041 LATIN CAPITAL LETTER A to U+005A LATIN CAPITAL LETTER Z, or U+0061 LATIN SMALL LETTER A to U+007A LATIN SMALL LETTER Z, then, for historical reasons, all the characters that were matched after the U+0026 AMPERSAND character (&) must be unconsumed, and nothing is returned.

Otherwise, return a character token for the character corresponding to the character reference name (as given by the second column of the named character references table).

If the markup contains I'm &notit; I tell you, the character reference is parsed as "not", as in, I'm ¬it; I tell you. But if the markup was I'm ∉ I tell you, the character reference would be parsed as "notin;", resulting in I'm ∉ I tell you.

8.2.5 Tree construction

Status: Last call for comments

The input to the tree construction stage is a sequence of tokens from the tokenization stage. The tree construction stage is associated with a DOM Document object when a parser is created. The "output" of this stage consists of dynamically modifying or extending that document's DOM tree.

This specification does not define when an interactive user agent has to render the Document so that it is available to the user, or when it has to begin accepting user input.

As each token is emitted from the tokenizer, the user agent must process the token according to the rules given in the section corresponding to the current insertion mode.

When the steps below require the UA to insert a character into a node, if that node has a child immediately before where the character is to be inserted, and that child is a Text node, and that Text node was the last node that the parser inserted into the document, then the character must be appended to that Text node; otherwise, a new Text node whose data is just that character must be inserted in the appropriate place.

Here are some sample inputs to the parser and the corresponding number of text nodes that they result in, assuming a user agent that executes scripts.

Input	Number of text nodes
A<script> var script = document.getElementsByTagName('script')[0]; document.body.removeChild(script); </script>B	Two adjacent text nodes in the document, containing "A" and "B".
A<script> var text = document.createTextNode('B'); document.body.appendChild(text); </script>C	Four text nodes; "A" before the script, the script's contents, "B" after the script, and then, immediately after that, "C".
A<script> var text = document.getElementsByTagName('script')[0].firstChild; text.data = 'B'; document.body.appendChild(text); </script>B	Two adjacent text nodes in the document, containing "A" and "BB".
A<table>B<tr>C</tr>C</table>	Three adjacent text nodes before the table, containing "A", "B", and "CC" respectively. (This is caused by foster parenting.)
A<table><tr> B</tr> B</table>	Two adjacent text nodes before the table, containing "A" and " B B" (space-B-space-B) respectively. (This is caused by foster parenting.)
A<table><tr> B</tr> </em>C</table>	Three adjacent text nodes before the table, containing "A", " B" (space-B), and "C" respectively, and one text node inside the table (as a child of a `tbody`) with a single space character. (Space characters separated from non-space characters by non-character tokens are not affected by foster parenting, even if those other tokens then get ignored.)

DOM mutation events must not fire for changes caused by the UA parsing the document. (Conceptually, the parser is not mutating the DOM, it is constructing it.) This includes the parsing of any content inserted using document.write() and document.writeln() calls. [DOMEVENTS]

Not all of the tag names mentioned below are conformant tag names in this specification; many are included to handle legacy content. They still form part of the algorithm that implementations are required to implement to claim conformance.

The algorithm described below places no limit on the depth of the DOM tree generated, or on the length of tag names, attribute names, attribute values, text nodes, etc. While implementors are encouraged to avoid arbitrary limits, it is recognized that practical concerns will likely force user agents to impose nesting depth constraints.

8.2.5.1 Creating and inserting elements

Status: Last call for comments

When the steps below require the UA to create an element for a token in a particular namespace, the UA must create a node implementing the interface appropriate for the element type corresponding to the tag name of the token in the given namespace (as given in the specification that defines that element, e.g. for an a element in the HTML namespace, this specification defines it to be the HTMLAnchorElement interface), with the tag name being the name of that element, with the node being in the given namespace, and with the attributes on the node being those given in the given token.

The interface appropriate for an element in the HTML namespace that is not defined in this specification (or other applicable specifications) is HTMLUnknownElement. Element in other namespaces whose interface is not defined by that namespace's specification must use the interface Element.

When a resettable element is created in this manner, its reset algorithm must be invoked once the attributes are set. (This initializes the element's value and checkedness based on the element's attributes.)

When the steps below require the UA to insert an HTML element for a token, the UA must first create an element for the token in the HTML namespace, and then append this node to the current node, and push it onto the stack of open elements so that it is the new current node.

The steps below may also require that the UA insert an HTML element in a particular place, in which case the UA must follow the same steps except that it must insert or append the new node in the location specified instead of appending it to the current node. (This happens in particular during the parsing of tables with invalid content.)

If an element created by the insert an HTML element algorithm is a form-associated element, and the form element pointer is not null, and the newly created element doesn't have a form attribute, the user agent must associate the newly created element with the form element pointed to by the form element pointer before inserting it wherever it is to be inserted.

When the steps below require the UA to insert a foreign element for a token, the UA must first create an element for the token in the given namespace, and then append this node to the current node, and push it onto the stack of open elements so that it is the new current node. If the newly created element has an xmlns attribute in the XMLNS namespace whose value is not exactly the same as the element's namespace, that is a parse error. Similarly, if the newly created element has an xmlns:xlink attribute in the XMLNS namespace whose value is not the XLink Namespace, that is a parse error.

When the steps below require the user agent to adjust MathML attributes for a token, then, if the token has an attribute named definitionurl, change its name to definitionURL (note the case difference).

When the steps below require the user agent to adjust SVG attributes for a token, then, for each attribute on the token whose attribute name is one of the ones in the first column of the following table, change the attribute's name to the name given in the corresponding cell in the second column. (This fixes the case of SVG attributes that are not all lowercase.)

Attribute name on token	Attribute name on element
`attributename`	`attributeName`
`attributetype`	`attributeType`
`basefrequency`	`baseFrequency`
`baseprofile`	`baseProfile`
`calcmode`	`calcMode`
`clippathunits`	`clipPathUnits`
`contentscripttype`	`contentScriptType`
`contentstyletype`	`contentStyleType`
`diffuseconstant`	`diffuseConstant`
`edgemode`	`edgeMode`
`externalresourcesrequired`	`externalResourcesRequired`
`filterres`	`filterRes`
`filterunits`	`filterUnits`
`glyphref`	`glyphRef`
`gradienttransform`	`gradientTransform`
`gradientunits`	`gradientUnits`
`kernelmatrix`	`kernelMatrix`
`kernelunitlength`	`kernelUnitLength`
`keypoints`	`keyPoints`
`keysplines`	`keySplines`
`keytimes`	`keyTimes`
`lengthadjust`	`lengthAdjust`
`limitingconeangle`	`limitingConeAngle`
`markerheight`	`markerHeight`
`markerunits`	`markerUnits`
`markerwidth`	`markerWidth`
`maskcontentunits`	`maskContentUnits`
`maskunits`	`maskUnits`
`numoctaves`	`numOctaves`
`pathlength`	`pathLength`
`patterncontentunits`	`patternContentUnits`
`patterntransform`	`patternTransform`
`patternunits`	`patternUnits`
`pointsatx`	`pointsAtX`
`pointsaty`	`pointsAtY`
`pointsatz`	`pointsAtZ`
`preservealpha`	`preserveAlpha`
`preserveaspectratio`	`preserveAspectRatio`
`primitiveunits`	`primitiveUnits`
`refx`	`refX`
`refy`	`refY`
`repeatcount`	`repeatCount`
`repeatdur`	`repeatDur`
`requiredextensions`	`requiredExtensions`
`requiredfeatures`	`requiredFeatures`
`specularconstant`	`specularConstant`
`specularexponent`	`specularExponent`
`spreadmethod`	`spreadMethod`
`startoffset`	`startOffset`
`stddeviation`	`stdDeviation`
`stitchtiles`	`stitchTiles`
`surfacescale`	`surfaceScale`
`systemlanguage`	`systemLanguage`
`tablevalues`	`tableValues`
`targetx`	`targetX`
`targety`	`targetY`
`textlength`	`textLength`
`viewbox`	`viewBox`
`viewtarget`	`viewTarget`
`xchannelselector`	`xChannelSelector`
`ychannelselector`	`yChannelSelector`
`zoomandpan`	`zoomAndPan`

When the steps below require the user agent to adjust foreign attributes for a token, then, if any of the attributes on the token match the strings given in the first column of the following table, let the attribute be a namespaced attribute, with the prefix being the string given in the corresponding cell in the second column, the local name being the string given in the corresponding cell in the third column, and the namespace being the namespace given in the corresponding cell in the fourth column. (This fixes the use of namespaced attributes, in particular lang attributes in the XML namespace.)

Attribute name	Prefix	Local name	Namespace
`xlink:actuate`	`xlink`	`actuate`	XLink namespace
`xlink:arcrole`	`xlink`	`arcrole`	XLink namespace
`xlink:href`	`xlink`	`href`	XLink namespace
`xlink:role`	`xlink`	`role`	XLink namespace
`xlink:show`	`xlink`	`show`	XLink namespace
`xlink:title`	`xlink`	`title`	XLink namespace
`xlink:type`	`xlink`	`type`	XLink namespace
`xml:base`	`xml`	`base`	XML namespace
`xml:lang`	`xml`	`lang`	XML namespace
`xml:space`	`xml`	`space`	XML namespace
`xmlns`	(none)	`xmlns`	XMLNS namespace
`xmlns:xlink`	`xmlns`	`xlink`	XMLNS namespace

The generic raw text element parsing algorithm and the generic RCDATA element parsing algorithm consist of the following steps. These algorithms are always invoked in response to a start tag token.

Insert an HTML element for the token.
If the algorithm that was invoked is the generic raw text element parsing algorithm, switch the tokenizer to the RAWTEXT state; otherwise the algorithm invoked was the generic RCDATA element parsing algorithm, switch the tokenizer to the RCDATA state.
Let the original insertion mode be the current insertion mode.
Then, switch the insertion mode to "text".

8.2.5.2 Closing elements that have implied end tags

Status: Last call for comments

When the steps below require the UA to generate implied end tags, then, while the current node is a dd element, a dt element, an li element, an option element, an optgroup element, a p element, an rp element, or an rt element, the UA must pop the current node off the stack of open elements.

If a step requires the UA to generate implied end tags but lists an element to exclude from the process, then the UA must perform the above steps as if that element was not in the above list.

8.2.5.3 Foster parenting

Status: Last call for comments

Foster parenting happens when content is misnested in tables.

When a node node is to be foster parented, the node node must be inserted into the foster parent element.

The foster parent element is the parent element of the last table element in the stack of open elements, if there is a table element and it has such a parent element. If there is no table element in the stack of open elements (fragment case), then the foster parent element is the first element in the stack of open elements (the html element). Otherwise, if there is a table element in the stack of open elements, but the last table element in the stack of open elements has no parent, or its parent node is not an element, then the foster parent element is the element before the last table element in the stack of open elements.

If the foster parent element is the parent element of the last table element in the stack of open elements, then node must be inserted immediately before the last table element in the stack of open elements in the foster parent element; otherwise, node must be appended to the foster parent element.

8.2.5.4 The "initial" insertion mode

Status: Last call for comments

When the insertion mode is "initial", tokens must be handled as follows:

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), or U+0020 SPACE

Ignore the token.

A comment token

Append a Comment node to the Document object with the data attribute set to the data given in the comment token.

A DOCTYPE token

If the DOCTYPE token's name is not a case-sensitive match for the string "html", or the token's public identifier is not missing, or the token's system identifier is neither missing nor a case-sensitive match for the string "about:legacy-compat", and none of the sets of conditions in the following list are matched, then there is a parse error.

The DOCTYPE token's name is a case-sensitive match for the string "html", the token's public identifier is the case-sensitive string "-//W3C//DTD HTML 4.0//EN", and the token's system identifier is either missing or the case-sensitive string "http://www.w3.org/TR/REC-html40/strict.dtd".
The DOCTYPE token's name is a case-sensitive match for the string "html", the token's public identifier is the case-sensitive string "-//W3C//DTD HTML 4.01//EN", and the token's system identifier is either missing or the case-sensitive string "http://www.w3.org/TR/html4/strict.dtd".
The DOCTYPE token's name is a case-sensitive match for the string "html", the token's public identifier is the case-sensitive string "-//W3C//DTD XHTML 1.0 Strict//EN", and the token's system identifier is the case-sensitive string "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd".
The DOCTYPE token's name is a case-sensitive match for the string "html", the token's public identifier is the case-sensitive string "-//W3C//DTD XHTML 1.1//EN", and the token's system identifier is the case-sensitive string "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd".

Conformance checkers may, based on the values (including presence or lack thereof) of the DOCTYPE token's name, public identifier, or system identifier, switch to a conformance checking mode for another language (e.g. based on the DOCTYPE token a conformance checker could recognize that the document is an HTML4-era document, and defer to an HTML4 conformance checker.)

Append a DocumentType node to the Document node, with the name attribute set to the name given in the DOCTYPE token, or the empty string if the name was missing; the publicId attribute set to the public identifier given in the DOCTYPE token, or the empty string if the public identifier was missing; the systemId attribute set to the system identifier given in the DOCTYPE token, or the empty string if the system identifier was missing; and the other attributes specific to DocumentType objects set to null and empty lists as appropriate. Associate the DocumentType node with the Document object so that it is returned as the value of the doctype attribute of the Document object.

Then, if the DOCTYPE token matches one of the conditions in the following list, then set the Document to quirks mode:

The force-quirks flag is set to on.
The name is set to anything other than "html" (compared case-sensitively).
The public identifier starts with: "+//Silmaril//dtd html Pro v0r11 19970101//"
The public identifier starts with: "-//AdvaSoft Ltd//DTD HTML 3.0 asWedit + extensions//"
The public identifier starts with: "-//AS//DTD HTML 3.0 asWedit + extensions//"
The public identifier starts with: "-//IETF//DTD HTML 2.0 Level 1//"
The public identifier starts with: "-//IETF//DTD HTML 2.0 Level 2//"
The public identifier starts with: "-//IETF//DTD HTML 2.0 Strict Level 1//"
The public identifier starts with: "-//IETF//DTD HTML 2.0 Strict Level 2//"
The public identifier starts with: "-//IETF//DTD HTML 2.0 Strict//"
The public identifier starts with: "-//IETF//DTD HTML 2.0//"
The public identifier starts with: "-//IETF//DTD HTML 2.1E//"
The public identifier starts with: "-//IETF//DTD HTML 3.0//"
The public identifier starts with: "-//IETF//DTD HTML 3.2 Final//"
The public identifier starts with: "-//IETF//DTD HTML 3.2//"
The public identifier starts with: "-//IETF//DTD HTML 3//"
The public identifier starts with: "-//IETF//DTD HTML Level 0//"
The public identifier starts with: "-//IETF//DTD HTML Level 1//"
The public identifier starts with: "-//IETF//DTD HTML Level 2//"
The public identifier starts with: "-//IETF//DTD HTML Level 3//"
The public identifier starts with: "-//IETF//DTD HTML Strict Level 0//"
The public identifier starts with: "-//IETF//DTD HTML Strict Level 1//"
The public identifier starts with: "-//IETF//DTD HTML Strict Level 2//"
The public identifier starts with: "-//IETF//DTD HTML Strict Level 3//"
The public identifier starts with: "-//IETF//DTD HTML Strict//"
The public identifier starts with: "-//IETF//DTD HTML//"
The public identifier starts with: "-//Metrius//DTD Metrius Presentational//"
The public identifier starts with: "-//Microsoft//DTD Internet Explorer 2.0 HTML Strict//"
The public identifier starts with: "-//Microsoft//DTD Internet Explorer 2.0 HTML//"
The public identifier starts with: "-//Microsoft//DTD Internet Explorer 2.0 Tables//"
The public identifier starts with: "-//Microsoft//DTD Internet Explorer 3.0 HTML Strict//"
The public identifier starts with: "-//Microsoft//DTD Internet Explorer 3.0 HTML//"
The public identifier starts with: "-//Microsoft//DTD Internet Explorer 3.0 Tables//"
The public identifier starts with: "-//Netscape Comm. Corp.//DTD HTML//"
The public identifier starts with: "-//Netscape Comm. Corp.//DTD Strict HTML//"
The public identifier starts with: "-//O'Reilly and Associates//DTD HTML 2.0//"
The public identifier starts with: "-//O'Reilly and Associates//DTD HTML Extended 1.0//"
The public identifier starts with: "-//O'Reilly and Associates//DTD HTML Extended Relaxed 1.0//"
The public identifier starts with: "-//SoftQuad Software//DTD HoTMetaL PRO 6.0::19990601::extensions to HTML 4.0//"
The public identifier starts with: "-//SoftQuad//DTD HoTMetaL PRO 4.0::19971010::extensions to HTML 4.0//"
The public identifier starts with: "-//Spyglass//DTD HTML 2.0 Extended//"
The public identifier starts with: "-//SQ//DTD HTML 2.0 HoTMetaL + extensions//"
The public identifier starts with: "-//Sun Microsystems Corp.//DTD HotJava HTML//"
The public identifier starts with: "-//Sun Microsystems Corp.//DTD HotJava Strict HTML//"
The public identifier starts with: "-//W3C//DTD HTML 3 1995-03-24//"
The public identifier starts with: "-//W3C//DTD HTML 3.2 Draft//"
The public identifier starts with: "-//W3C//DTD HTML 3.2 Final//"
The public identifier starts with: "-//W3C//DTD HTML 3.2//"
The public identifier starts with: "-//W3C//DTD HTML 3.2S Draft//"
The public identifier starts with: "-//W3C//DTD HTML 4.0 Frameset//"
The public identifier starts with: "-//W3C//DTD HTML 4.0 Transitional//"
The public identifier starts with: "-//W3C//DTD HTML Experimental 19960712//"
The public identifier starts with: "-//W3C//DTD HTML Experimental 970421//"
The public identifier starts with: "-//W3C//DTD W3 HTML//"
The public identifier starts with: "-//W3O//DTD W3 HTML 3.0//"
The public identifier is set to: "-//W3O//DTD W3 HTML Strict 3.0//EN//"
The public identifier starts with: "-//WebTechs//DTD Mozilla HTML 2.0//"
The public identifier starts with: "-//WebTechs//DTD Mozilla HTML//"
The public identifier is set to: "-/W3C/DTD HTML 4.0 Transitional/EN"
The public identifier is set to: "HTML"
The system identifier is set to: "http://www.ibm.com/data/dtd/v11/ibmxhtml1-transitional.dtd"
The system identifier is missing and the public identifier starts with: "-//W3C//DTD HTML 4.01 Frameset//"
The system identifier is missing and the public identifier starts with: "-//W3C//DTD HTML 4.01 Transitional//"

Otherwise, if the DOCTYPE token matches one of the conditions in the following list, then set the Document to limited quirks mode:

The public identifier starts with: "-//W3C//DTD XHTML 1.0 Frameset//"
The public identifier starts with: "-//W3C//DTD XHTML 1.0 Transitional//"
The system identifier is not missing and the public identifier starts with: "-//W3C//DTD HTML 4.01 Frameset//"
The system identifier is not missing and the public identifier starts with: "-//W3C//DTD HTML 4.01 Transitional//"

The system identifier and public identifier strings must be compared to the values given in the lists above in an ASCII case-insensitive manner. A system identifier whose value is the empty string is not considered missing for the purposes of the conditions above.

Then, switch the insertion mode to "before html".

Anything else

If the document is not an iframe srcdoc document, then this is a parse error; set the Document to quirks mode.

In any case, switch the insertion mode to "before html", then reprocess the current token.

8.2.5.5 The "before html" insertion mode

Status: Last call for comments

When the insertion mode is "before html", tokens must be handled as follows:

A DOCTYPE token

Parse error. Ignore the token.

A comment token

Append a Comment node to the Document object with the data attribute set to the data given in the comment token.

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), or U+0020 SPACE

Ignore the token.

A start tag whose tag name is "html"

Create an element for the token in the HTML namespace. Append it to the Document object. Put this element in the stack of open elements.

If the Document is being loaded as part of navigation of a browsing context, then: if the newly created element has a manifest attribute, then resolve the value of that attribute to an absolute URL, relative to the newly created element, and if that is successful, run the application cache selection algorithm with the resulting absolute URL with any <fragment> component removed; otherwise, if there is no such attribute or resolving it fails, run the application cache selection algorithm with no manifest. The algorithm must be passed the Document object.

Switch the insertion mode to "before head".

An end tag whose tag name is one of: "head", "body", "html", "br"

Act as described in the "anything else" entry below.

Any other end tag

Parse error. Ignore the token.

Anything else

Create an html element. Append it to the Document object. Put this element in the stack of open elements.

If the Document is being loaded as part of navigation of a browsing context, then: run the application cache selection algorithm with no manifest, passing it the Document object.

Switch the insertion mode to "before head", then reprocess the current token.

The root element can end up being removed from the Document object, e.g. by scripts; nothing in particular happens in such cases, content continues being appended to the nodes as described in the next section.

8.2.5.6 The "before head" insertion mode

Status: Last call for comments

When the insertion mode is "before head", tokens must be handled as follows:

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), or U+0020 SPACE

Ignore the token.

A comment token

Append a Comment node to the current node with the data attribute set to the data given in the comment token.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is "html"

Process the token using the rules for the "in body" insertion mode.

A start tag whose tag name is "head"

Insert an HTML element for the token.

Set the head element pointer to the newly created head element.

Switch the insertion mode to "in head".

An end tag whose tag name is one of: "head", "body", "html", "br"

Act as if a start tag token with the tag name "head" and no attributes had been seen, then reprocess the current token.

Any other end tag

Parse error. Ignore the token.

Anything else

Act as if a start tag token with the tag name "head" and no attributes had been seen, then reprocess the current token.

8.2.5.7 The "in head" insertion mode

Status: Last call for comments

When the insertion mode is "in head", tokens must be handled as follows:

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), or U+0020 SPACE

A comment token

Append a Comment node to the current node with the data attribute set to the data given in the comment token.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is "html"

Process the token using the rules for the "in body" insertion mode.

A start tag whose tag name is one of: "base", "command", "link"

Insert an HTML element for the token. Immediately pop the current node off the stack of open elements.

Acknowledge the token's self-closing flag, if it is set.

A start tag whose tag name is "meta"

Insert an HTML element for the token. Immediately pop the current node off the stack of open elements.

Acknowledge the token's self-closing flag, if it is set.

If the element has a charset attribute, and its value is a supported encoding, and the confidence is currently tentative, then change the encoding to the encoding given by the value of the charset attribute.

Otherwise, if the element has a content attribute, and applying the algorithm for extracting an encoding from a Content-Type to its value returns a supported encoding encoding, and the confidence is currently tentative, then change the encoding to the encoding encoding.

A start tag whose tag name is "title"

Follow the generic RCDATA element parsing algorithm.

A start tag whose tag name is "noscript", if the scripting flag is enabled

A start tag whose tag name is one of: "noframes", "style"

Follow the generic raw text element parsing algorithm.

A start tag whose tag name is "noscript", if the scripting flag is disabled

Insert an HTML element for the token.

Switch the insertion mode to "in head noscript".

A start tag whose tag name is "script"

Run these steps:

Create an element for the token in the HTML namespace.
Mark the element as being "parser-inserted".

This ensures that, if the script is external, any document.write() calls in the script will execute in-line, instead of blowing the document away, as would happen in most other cases. It also prevents the script from executing until the end tag is seen.
If the parser was originally created for the HTML fragment parsing algorithm, then mark the script element as "already started". (fragment case)
Append the new element to the current node and push it onto the stack of open elements.
Switch the tokenizer to the script data state.
Let the original insertion mode be the current insertion mode.
Switch the insertion mode to "text".

An end tag whose tag name is "head"

Pop the current node (which will be the head element) off the stack of open elements.

Switch the insertion mode to "after head".

An end tag whose tag name is one of: "body", "html", "br"

Act as described in the "anything else" entry below.

A start tag whose tag name is "head"

Any other end tag

Parse error. Ignore the token.

Anything else

Act as if an end tag token with the tag name "head" had been seen, and reprocess the current token.

8.2.5.8 The "in head noscript" insertion mode

Status: Last call for comments

When the insertion mode is "in head noscript", tokens must be handled as follows:

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is "html"

Process the token using the rules for the "in body" insertion mode.

An end tag whose tag name is "noscript"

Pop the current node (which will be a noscript element) from the stack of open elements; the new current node will be a head element.

Switch the insertion mode to "in head".

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), or U+0020 SPACE

A comment token

A start tag whose tag name is one of: "link", "meta", "noframes", "style"

Process the token using the rules for the "in head" insertion mode.

An end tag whose tag name is "br"

Act as described in the "anything else" entry below.

A start tag whose tag name is one of: "head", "noscript"

Any other end tag

Parse error. Ignore the token.

Anything else

Parse error. Act as if an end tag with the tag name "noscript" had been seen and reprocess the current token.

8.2.5.9 The "after head" insertion mode

Status: Last call for comments

When the insertion mode is "after head", tokens must be handled as follows:

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), or U+0020 SPACE

A comment token

Append a Comment node to the current node with the data attribute set to the data given in the comment token.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is "html"

Process the token using the rules for the "in body" insertion mode.

A start tag whose tag name is "body"

Insert an HTML element for the token.

Set the frameset-ok flag to "not ok".

Switch the insertion mode to "in body".

A start tag whose tag name is "frameset"

Insert an HTML element for the token.

Switch the insertion mode to "in frameset".

A start tag token whose tag name is one of: "base", "link", "meta", "noframes", "script", "style", "title"

Push the node pointed to by the head element pointer onto the stack of open elements.

Process the token using the rules for the "in head" insertion mode.

Remove the node pointed to by the head element pointer from the stack of open elements.

The head element pointer cannot be null at this point.

An end tag whose tag name is one of: "body", "html", "br"

Act as described in the "anything else" entry below.

A start tag whose tag name is "head"

Any other end tag

Parse error. Ignore the token.

Anything else

Act as if a start tag token with the tag name "body" and no attributes had been seen, then set the frameset-ok flag back to "ok", and then reprocess the current token.

8.2.5.10 The "in body" insertion mode

Status: Last call for comments

When the insertion mode is "in body", tokens must be handled as follows:

A character token

Reconstruct the active formatting elements, if any.

Insert the token's character into the current node.

If the token is not one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), or U+0020 SPACE, then set the frameset-ok flag to "not ok".

A comment token

Append a Comment node to the current node with the data attribute set to the data given in the comment token.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is "html"

Parse error. For each attribute on the token, check to see if the attribute is already present on the top element of the stack of open elements. If it is not, add the attribute and its corresponding value to that element.

A start tag token whose tag name is one of: "base", "command", "link", "meta", "noframes", "script", "style", "title"

Process the token using the rules for the "in head" insertion mode.

A start tag whose tag name is "body"

If the second element on the stack of open elements is not a body element, or, if the stack of open elements has only one node on it, then ignore the token. (fragment case)

Otherwise, for each attribute on the token, check to see if the attribute is already present on the body element (the second element) on the stack of open elements. If it is not, add the attribute and its corresponding value to that element.

A start tag whose tag name is "frameset"

If the second element on the stack of open elements is not a body element, or, if the stack of open elements has only one node on it, then ignore the token. (fragment case)

If the frameset-ok flag is set to "not ok", ignore the token.

Otherwise, run the following steps:

Remove the second element on the stack of open elements from its parent node, if it has one.
Pop all the nodes from the bottom of the stack of open elements, from the current node up to, but not including, the root html element.
Insert an HTML element for the token.
Switch the insertion mode to "in frameset".

An end-of-file token

If there is a node in the stack of open elements that is not either a dd element, a dt element, an li element, a p element, a tbody element, a td element, a tfoot element, a th element, a thead element, a tr element, the body element, or the html element, then this is a parse error.

An end tag whose tag name is "body"

If the stack of open elements does not have a body element in scope, this is a parse error; ignore the token.

Otherwise, if there is a node in the stack of open elements that is not either a dd element, a dt element, an li element, an optgroup element, an option element, a p element, an rp element, an rt element, a tbody element, a td element, a tfoot element, a th element, a thead element, a tr element, the body element, or the html element, then this is a parse error.

Switch the insertion mode to "after body".

An end tag whose tag name is "html"

Act as if an end tag with tag name "body" had been seen, then, if that token wasn't ignored, reprocess the current token.

A start tag whose tag name is one of: "address", "article", "aside", "blockquote", "center", "details", "dir", "div", "dl", "fieldset", "figure", "footer", "header", "hgroup", "menu", "nav", "ol", "p", "section", "ul"

If the stack of open elements has a p element in scope, then act as if an end tag with the tag name "p" had been seen.

Insert an HTML element for the token.

A start tag whose tag name is one of: "h1", "h2", "h3", "h4", "h5", "h6"

If the stack of open elements has a p element in scope, then act as if an end tag with the tag name "p" had been seen.

If the current node is an element whose tag name is one of "h1", "h2", "h3", "h4", "h5", or "h6", then this is a parse error; pop the current node off the stack of open elements.

Insert an HTML element for the token.

A start tag whose tag name is one of: "pre", "listing"

If the stack of open elements has a p element in scope, then act as if an end tag with the tag name "p" had been seen.

Insert an HTML element for the token.

If the next token is a U+000A LINE FEED (LF) character token, then ignore that token and move on to the next one. (Newlines at the start of pre blocks are ignored as an authoring convenience.)

Set the frameset-ok flag to "not ok".

A start tag whose tag name is "form"

If the form element pointer is not null, then this is a parse error; ignore the token.

Otherwise:

If the stack of open elements has a p element in scope, then act as if an end tag with the tag name "p" had been seen.

Insert an HTML element for the token, and set the form element pointer to point to the element created.

A start tag whose tag name is "li"

Run these steps:

Set the frameset-ok flag to "not ok".
Initialize node to be the current node (the bottommost node of the stack).
Loop: If node is an li element, then act as if an end tag with the tag name "li" had been seen, then jump to the last step.
If node is not in the formatting category, and is not in the phrasing category, and is not an address, div, or p element, then jump to the last step.
Otherwise, set node to the previous entry in the stack of open elements and return to the step labeled loop.
This is the last step.

If the stack of open elements has a p element in scope, then act as if an end tag with the tag name "p" had been seen.

Finally, insert an HTML element for the token.

A start tag whose tag name is one of: "dd", "dt"

Run these steps:

Set the frameset-ok flag to "not ok".
Initialize node to be the current node (the bottommost node of the stack).
Loop: If node is a dd or dt element, then act as if an end tag with the same tag name as node had been seen, then jump to the last step.
If node is not in the formatting category, and is not in the phrasing category, and is not an address, div, or p element, then jump to the last step.
Otherwise, set node to the previous entry in the stack of open elements and return to the step labeled loop.
This is the last step.

If the stack of open elements has a p element in scope, then act as if an end tag with the tag name "p" had been seen.

Finally, insert an HTML element for the token.

A start tag whose tag name is "plaintext"

If the stack of open elements has a p element in scope, then act as if an end tag with the tag name "p" had been seen.

Insert an HTML element for the token.

Switch the tokenizer to the PLAINTEXT state.

Once a start tag with the tag name "plaintext" has been seen, that will be the last token ever seen other than character tokens (and the end-of-file token), because there is no way to switch out of the PLAINTEXT state.

An end tag whose tag name is one of: "address", "article", "aside", "blockquote", "center", "details", "dir", "div", "dl", "fieldset", "figure", "footer", "header", "hgroup", "listing", "menu", "nav", "ol", "pre", "section", "ul"

If the stack of open elements does not have an element in scope with the same tag name as that of the token, then this is a parse error; ignore the token.

Otherwise, run these steps:

Generate implied end tags.
If the current node is not an element with the same tag name as that of the token, then this is a parse error.
Pop elements from the stack of open elements until an element with the same tag name as the token has been popped from the stack.

An end tag whose tag name is "form"

Let node be the element that the form element pointer is set to.

Set the form element pointer to null.

If node is null or the stack of open elements does not have node in scope, then this is a parse error; ignore the token.

Otherwise, run these steps:

Generate implied end tags.
If the current node is not node, then this is a parse error.
Remove node from the stack of open elements.

An end tag whose tag name is "p"

If the stack of open elements does not have an element in scope with the same tag name as that of the token, then this is a parse error; act as if a start tag with the tag name "p" had been seen, then reprocess the current token.

Otherwise, run these steps:

Generate implied end tags, except for elements with the same tag name as the token.
If the current node is not an element with the same tag name as that of the token, then this is a parse error.
Pop elements from the stack of open elements until an element with the same tag name as the token has been popped from the stack.

An end tag whose tag name is "li"

If the stack of open elements does not have an element in list item scope with the same tag name as that of the token, then this is a parse error; ignore the token.

Otherwise, run these steps:

Generate implied end tags, except for elements with the same tag name as the token.
If the current node is not an element with the same tag name as that of the token, then this is a parse error.
Pop elements from the stack of open elements until an element with the same tag name as the token has been popped from the stack.

An end tag whose tag name is one of: "dd", "dt"

If the stack of open elements does not have an element in scope with the same tag name as that of the token, then this is a parse error; ignore the token.

Otherwise, run these steps:

Generate implied end tags, except for elements with the same tag name as the token.
If the current node is not an element with the same tag name as that of the token, then this is a parse error.
Pop elements from the stack of open elements until an element with the same tag name as the token has been popped from the stack.

An end tag whose tag name is one of: "h1", "h2", "h3", "h4", "h5", "h6"

If the stack of open elements does not have an element in scope whose tag name is one of "h1", "h2", "h3", "h4", "h5", or "h6", then this is a parse error; ignore the token.

Otherwise, run these steps:

Generate implied end tags.
If the current node is not an element with the same tag name as that of the token, then this is a parse error.
Pop elements from the stack of open elements until an element whose tag name is one of "h1", "h2", "h3", "h4", "h5", or "h6" has been popped from the stack.

An end tag whose tag name is "sarcasm"

Take a deep breath, then act as described in the "any other end tag" entry below.

A start tag whose tag name is "a"

If the list of active formatting elements contains an element whose tag name is "a" between the end of the list and the last marker on the list (or the start of the list if there is no marker on the list), then this is a parse error; act as if an end tag with the tag name "a" had been seen, then remove that element from the list of active formatting elements and the stack of open elements if the end tag didn't already remove it (it might not have if the element is not in table scope).

In the non-conforming stream <a href="a">a<table><a href="b">b</table>x, the first a element would be closed upon seeing the second one, and the "x" character would be inside a link to "b", not to "a". This is despite the fact that the outer a element is not in table scope (meaning that a regular </a> end tag at the start of the table wouldn't close the outer a element).

Reconstruct the active formatting elements, if any.

Insert an HTML element for the token. Add that element to the list of active formatting elements.

A start tag whose tag name is one of: "b", "big", "code", "em", "font", "i", "s", "small", "strike", "strong", "tt", "u"

Reconstruct the active formatting elements, if any.

Insert an HTML element for the token. Add that element to the list of active formatting elements.

A start tag whose tag name is "nobr"

Reconstruct the active formatting elements, if any.

If the stack of open elements has a nobr element in scope, then this is a parse error; act as if an end tag with the tag name "nobr" had been seen, then once again reconstruct the active formatting elements, if any.

Insert an HTML element for the token. Add that element to the list of active formatting elements.

An end tag whose tag name is one of: "a", "b", "big", "code", "em", "font", "i", "nobr", "s", "small", "strike", "strong", "tt", "u"

Run these steps:

Let the formatting element be the last element in the list of active formatting elements that:
- is between the end of the list and the last scope marker in the list, if any, or the start of the list otherwise, and
- has the same tag name as the token.
If there is no such node, or, if that node is also in the stack of open elements but the element is not in scope, then this is a parse error; ignore the token, and abort these steps.

Otherwise, if there is such a node, but that node is not in the stack of open elements, then this is a parse error; remove the element from the list, and abort these steps.

Otherwise, there is a formatting element and that element is in the stack and is in scope. If the element is not the current node, this is a parse error. In any case, proceed with the algorithm as written in the following steps.
Let the furthest block be the topmost node in the stack of open elements that is lower in the stack than the formatting element, and is not an element in the phrasing or formatting categories. There might not be one.
If there is no furthest block, then the UA must skip the subsequent steps and instead just pop all the nodes from the bottom of the stack of open elements, from the current node up to and including the formatting element, and remove the formatting element from the list of active formatting elements.
Let the common ancestor be the element immediately above the formatting element in the stack of open elements.
Let a bookmark note the position of the formatting element in the list of active formatting elements relative to the elements on either side of it in the list.
Let node and last node be the furthest block. Follow these steps:
1. Let node be the element immediately above node in the stack of open elements, or if node is no longer in the stack of open elements (e.g. because it got removed by the next step), the element that was immediately above node in the stack of open elements before node was removed.
2. If node is not in the list of active formatting elements, then remove node from the stack of open elements and then go back to step 1.
3. Otherwise, if node is the formatting element, then go to the next step in the overall algorithm.
4. Otherwise, if last node is the furthest block, then move the aforementioned bookmark to be immediately after the node in the list of active formatting elements.
5. Create an element for the token for which the element node was created, replace the entry for node in the list of active formatting elements with an entry for the new element, replace the entry for node in the stack of open elements with an entry for the new element, and let node be the new element.
6. Insert last node into node, first removing it from its previous parent node if any.
7. Let last node be node.
8. Return to step 1 of this inner set of steps.
If the common ancestor node is a table, tbody, tfoot, thead, or tr element, then, foster parent whatever last node ended up being in the previous step, first removing it from its previous parent node if any.

Otherwise, append whatever last node ended up being in the previous step to the common ancestor node, first removing it from its previous parent node if any.
Create an element for the token for which the formatting element was created.
Take all of the child nodes of the furthest block and append them to the element created in the last step.
Append that new element to the furthest block.
Remove the formatting element from the list of active formatting elements, and insert the new element into the list of active formatting elements at the position of the aforementioned bookmark.
Remove the formatting element from the stack of open elements, and insert the new element into the stack of open elements immediately below the position of the furthest block in that stack.
Jump back to step 1 in this series of steps.

Because of the way this algorithm causes elements to change parents, it has been dubbed the "adoption agency algorithm" (in contrast with other possible algorithms for dealing with misnested content, which included the "incest algorithm", the "secret affair algorithm", and the "Heisenberg algorithm").

A start tag whose tag name is "button"

If the stack of open elements has a button element in scope, then this is a parse error; act as if an end tag with the tag name "button" had been seen, then reprocess the token.

Otherwise:

Reconstruct the active formatting elements, if any.

Insert an HTML element for the token.

Insert a marker at the end of the list of active formatting elements.

Set the frameset-ok flag to "not ok".

A start tag token whose tag name is one of: "applet", "marquee", "object"

Reconstruct the active formatting elements, if any.

Insert an HTML element for the token.

Insert a marker at the end of the list of active formatting elements.

Set the frameset-ok flag to "not ok".

An end tag token whose tag name is one of: "applet", "button", "marquee", "object"

If the stack of open elements does not have an element in scope with the same tag name as that of the token, then this is a parse error; ignore the token.

Otherwise, run these steps:

Generate implied end tags.
If the current node is not an element with the same tag name as that of the token, then this is a parse error.
Pop elements from the stack of open elements until an element with the same tag name as the token has been popped from the stack.
Clear the list of active formatting elements up to the last marker.

A start tag whose tag name is "table"

If the Document is not set to quirks mode, and the stack of open elements has a p element in scope, then act as if an end tag with the tag name "p" had been seen.

Insert an HTML element for the token.

Set the frameset-ok flag to "not ok".

Switch the insertion mode to "in table".

A start tag whose tag name is one of: "area", "basefont", "bgsound", "br", "embed", "img", "input", "keygen", "wbr"

Reconstruct the active formatting elements, if any.

Insert an HTML element for the token. Immediately pop the current node off the stack of open elements.

Acknowledge the token's self-closing flag, if it is set.

Set the frameset-ok flag to "not ok".

A start tag whose tag name is one of: "param", "source"

Insert an HTML element for the token. Immediately pop the current node off the stack of open elements.

Acknowledge the token's self-closing flag, if it is set.

A start tag whose tag name is "hr"

If the stack of open elements has a p element in scope, then act as if an end tag with the tag name "p" had been seen.

Insert an HTML element for the token. Immediately pop the current node off the stack of open elements.

Acknowledge the token's self-closing flag, if it is set.

Set the frameset-ok flag to "not ok".

A start tag whose tag name is "image"

Parse error. Change the token's tag name to "img" and reprocess it. (Don't ask.)

A start tag whose tag name is "isindex"

If the form element pointer is not null, then ignore the token.

Otherwise:

Acknowledge the token's self-closing flag, if it is set.

Act as if a start tag token with the tag name "form" had been seen.

If the token has an attribute called "action", set the action attribute on the resulting form element to the value of the "action" attribute of the token.

Act as if a start tag token with the tag name "hr" had been seen.

Act as if a start tag token with the tag name "label" had been seen.

Act as if a stream of character tokens had been seen (see below for what they should say).

Act as if a start tag token with the tag name "input" had been seen, with all the attributes from the "isindex" token except "name", "action", and "prompt". Set the name attribute of the resulting input element to the value "isindex".

Act as if a stream of character tokens had been seen (see below for what they should say).

Act as if an end tag token with the tag name "label" had been seen.

Act as if a start tag token with the tag name "hr" had been seen.

Act as if an end tag token with the tag name "form" had been seen.

If the token has an attribute with the name "prompt", then the first stream of characters must be the same string as given in that attribute, and the second stream of characters must be empty. Otherwise, the two streams of character tokens together should, together with the input element, express the equivalent of "This is a searchable index. Insert your search keywords here: (input field)" in the user's preferred language.

A start tag whose tag name is "textarea"

Run these steps:

Insert an HTML element for the token.
If the next token is a U+000A LINE FEED (LF) character token, then ignore that token and move on to the next one. (Newlines at the start of textarea elements are ignored as an authoring convenience.)
Switch the tokenizer to the RCDATA state.
Let the original insertion mode be the current insertion mode.
Set the frameset-ok flag to "not ok".
Switch the insertion mode to "text".

A start tag whose tag name is "xmp"

If the stack of open elements has a p element in scope, then act as if an end tag with the tag name "p" had been seen.

Reconstruct the active formatting elements, if any.

Set the frameset-ok flag to "not ok".

Follow the generic raw text element parsing algorithm.

A start tag whose tag name is "iframe"

Set the frameset-ok flag to "not ok".

Follow the generic raw text element parsing algorithm.

A start tag whose tag name is "noembed"

A start tag whose tag name is "noscript", if the scripting flag is enabled

Follow the generic raw text element parsing algorithm.

A start tag whose tag name is "select"

Reconstruct the active formatting elements, if any.

Insert an HTML element for the token.

Set the frameset-ok flag to "not ok".

If the insertion mode is one of in table", "in caption", "in column group", "in table body", "in row", or "in cell", then switch the insertion mode to "in select in table". Otherwise, switch the insertion mode to "in select".

A start tag whose tag name is one of: "optgroup", "option"

If the stack of open elements has an option element in scope, then act as if an end tag with the tag name "option" had been seen.

Reconstruct the active formatting elements, if any.

Insert an HTML element for the token.

A start tag whose tag name is one of: "rp", "rt"

If the stack of open elements has a ruby element in scope, then generate implied end tags. If the current node is not then a ruby element, this is a parse error; pop all the nodes from the current node up to the node immediately before the bottommost ruby element on the stack of open elements.

Insert an HTML element for the token.

An end tag whose tag name is "br"

Parse error. Act as if a start tag token with the tag name "br" had been seen. Ignore the end tag token.

A start tag whose tag name is "math"

Reconstruct the active formatting elements, if any.

Adjust MathML attributes for the token. (This fixes the case of MathML attributes that are not all lowercase.)

Adjust foreign attributes for the token. (This fixes the use of namespaced attributes, in particular XLink.)

Insert a foreign element for the token, in the MathML namespace.

If the token has its self-closing flag set, pop the current node off the stack of open elements and acknowledge the token's self-closing flag.

Otherwise, if the insertion mode is not already "in foreign content", let the secondary insertion mode be the current insertion mode, and then switch the insertion mode to "in foreign content".

A start tag whose tag name is "svg"

Reconstruct the active formatting elements, if any.

Adjust SVG attributes for the token. (This fixes the case of SVG attributes that are not all lowercase.)

Adjust foreign attributes for the token. (This fixes the use of namespaced attributes, in particular XLink in SVG.)

Insert a foreign element for the token, in the SVG namespace.

If the token has its self-closing flag set, pop the current node off the stack of open elements and acknowledge the token's self-closing flag.

Otherwise, if the insertion mode is not already "in foreign content", let the secondary insertion mode be the current insertion mode, and then switch the insertion mode to "in foreign content".

A start tag whose tag name is one of: "caption", "col", "colgroup", "frame", "head", "tbody", "td", "tfoot", "th", "thead", "tr"

Parse error. Ignore the token.

Any other start tag

Reconstruct the active formatting elements, if any.

Insert an HTML element for the token.

This element will be a phrasing element.

Any other end tag

Run these steps:

Initialize node to be the current node (the bottommost node of the stack).
If node has the same tag name as the token, then:
1. Generate implied end tags.
2. If the tag name of the end tag token does not match the tag name of the current node, this is a parse error.
3. Pop all the nodes from the current node up to node, including node, then stop these steps.
Otherwise, if node is in neither the formatting category nor the phrasing category, then this is a parse error; ignore the token, and abort these steps.
Set node to the previous entry in the stack of open elements.
Return to step 2.

8.2.5.11 The "text" insertion mode

Status: Last call for comments

When the insertion mode is "text", tokens must be handled as follows:

A character token

Insert the token's character into the current node.

An end-of-file token

Reset the insertion mode appropriately.

If the current node is a script element, mark the script element as "already started".

Pop the current node off the stack of open elements.

Switch the insertion mode to the original insertion mode and reprocess the current token.

An end tag whose tag name is "script"

Let script be the current node (which will be a script element).

Pop the current node off the stack of open elements.

Switch the insertion mode to the original insertion mode.

Let the old insertion point have the same value as the current insertion point. Let the insertion point be just before the next input character.

Increment the parser's script nesting level by one.

Run the script. This might cause some script to execute, which might cause new characters to be inserted into the tokenizer, and might cause the tokenizer to output more tokens, resulting in a reentrant invocation of the parser.

Decrement the parser's script nesting level by one. If the parser's script nesting level is zero, then set the parser pause flag to false.

Let the insertion point have the value of the old insertion point. (In other words, restore the insertion point to its previous value. This value might be the "undefined" value.)

At this stage, if there is a pending parsing-blocking script, then:

If the script nesting level is not zero:

Set the parser pause flag to true, and abort the processing of any nested invocations of the tokenizer, yielding control back to the caller. (Tokenization will resume when the caller returns to the "outer" tree construction stage.)

The tree construction stage of this particular parser is being called reentrantly, say from a call to document.write().

Otherwise:

Run these steps:

Let the script be the pending parsing-blocking script. There is no longer a pending parsing-blocking script.
Block the tokenizer for this instance of the HTML parser, such that the event loop will not run tasks that invoke the tokenizer.
Spin the event loop until there is no style sheet blocking scripts and the script's "ready to be parser-executed" flag is set.
Unblock the tokenizer for this instance of the HTML parser, such that tasks that invoke the tokenizer can again be run.
Let the insertion point be just before the next input character.
Increment the parser's script nesting level by one (it should be zero before this step, so this sets it to one).
Execute the script.
Decrement the parser's script nesting level by one. If the parser's script nesting level is zero (which it always should be at this point), then set the parser pause flag to false.
Let the insertion point be undefined again.
If there is once again a pending parsing-blocking script, then repeat these steps from step 1.

Any other end tag

Pop the current node off the stack of open elements.

Switch the insertion mode to the original insertion mode.

8.2.5.12 The "in table" insertion mode

Status: Last call for comments

When the insertion mode is "in table", tokens must be handled as follows:

A character token

Let the pending table character tokens be an empty list of tokens.

Let the original insertion mode be the current insertion mode.

Switch the insertion mode to "in table text" and reprocess the token.

A comment token

Append a Comment node to the current node with the data attribute set to the data given in the comment token.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is "caption"

Clear the stack back to a table context. (See below.)

Insert a marker at the end of the list of active formatting elements.

Insert an HTML element for the token, then switch the insertion mode to "in caption".

A start tag whose tag name is "colgroup"

Clear the stack back to a table context. (See below.)

Insert an HTML element for the token, then switch the insertion mode to "in column group".

A start tag whose tag name is "col"

Act as if a start tag token with the tag name "colgroup" had been seen, then reprocess the current token.

A start tag whose tag name is one of: "tbody", "tfoot", "thead"

Clear the stack back to a table context. (See below.)

Insert an HTML element for the token, then switch the insertion mode to "in table body".

A start tag whose tag name is one of: "td", "th", "tr"

Act as if a start tag token with the tag name "tbody" had been seen, then reprocess the current token.

A start tag whose tag name is "table"

Parse error. Act as if an end tag token with the tag name "table" had been seen, then, if that token wasn't ignored, reprocess the current token.

The fake end tag token here can only be ignored in the fragment case.

An end tag whose tag name is "table"

If the stack of open elements does not have an element in table scope with the same tag name as the token, this is a parse error. Ignore the token. (fragment case)

Otherwise:

Pop elements from this stack until a table element has been popped from the stack.

An end tag whose tag name is one of: "body", "caption", "col", "colgroup", "html", "tbody", "td", "tfoot", "th", "thead", "tr"

Parse error. Ignore the token.

A start tag whose tag name is one of: "style", "script"

Process the token using the rules for the "in head" insertion mode.

A start tag whose tag name is "input"

If the token does not have an attribute with the name "type", or if it does, but that attribute's value is not an ASCII case-insensitive match for the string "hidden", then: act as described in the "anything else" entry below.

Otherwise:

Insert an HTML element for the token.

Pop that input element off the stack of open elements.

A start tag whose tag name is "form"

If the form element pointer is not null, ignore the token.

Otherwise:

Insert an HTML element for the token.

Pop that form element off the stack of open elements.

An end-of-file token

If the current node is not the root html element, then this is a parse error.

It can only be the current node in the fragment case.

Generate implied end tags.

Anything else

Parse error. Process the token using the rules for the "in body" insertion mode, except that if the current node is a table, tbody, tfoot, thead, or tr element, then, whenever a node would be inserted into the current node, it must instead be foster parented.

When the steps above require the UA to clear the stack back to a table context, it means that the UA must, while the current node is not a table element or an html element, pop elements from the stack of open elements.

The current node being an html element after this process is a fragment case.

8.2.5.13 The "in table text" insertion mode

Status: Last call for comments

When the insertion mode is "in table text", tokens must be handled as follows:

A character token

Append the character token to the pending table character tokens list.

Anything else

If any of the tokens in the pending table character tokens list are character tokens that are not one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), or U+0020 SPACE, then reprocess those character tokens using the rules given in the "anything else" entry in the in table" insertion mode.

Otherwise, insert the characters given by the pending table character tokens list into the current node.

Switch the insertion mode to the original insertion mode and reprocess the token.

8.2.5.14 The "in caption" insertion mode

Status: Last call for comments

When the insertion mode is "in caption", tokens must be handled as follows:

An end tag whose tag name is "caption"

If the stack of open elements does not have an element in table scope with the same tag name as the token, this is a parse error. Ignore the token. (fragment case)

Otherwise:

Now, if the current node is not a caption element, then this is a parse error.

Pop elements from this stack until a caption element has been popped from the stack.

Clear the list of active formatting elements up to the last marker.

Switch the insertion mode to "in table".

A start tag whose tag name is one of: "caption", "col", "colgroup", "tbody", "td", "tfoot", "th", "thead", "tr"

An end tag whose tag name is "table"

Parse error. Act as if an end tag with the tag name "caption" had been seen, then, if that token wasn't ignored, reprocess the current token.

The fake end tag token here can only be ignored in the fragment case.

An end tag whose tag name is one of: "body", "col", "colgroup", "html", "tbody", "td", "tfoot", "th", "thead", "tr"

Parse error. Ignore the token.

Anything else

Process the token using the rules for the "in body" insertion mode.

8.2.5.15 The "in column group" insertion mode

Status: Last call for comments

When the insertion mode is "in column group", tokens must be handled as follows:

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), or U+0020 SPACE

Generate implied end tags.

A comment token

Append a Comment node to the current node with the data attribute set to the data given in the comment token.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is "html"

Process the token using the rules for the "in body" insertion mode.

A start tag whose tag name is "col"

Insert an HTML element for the token. Immediately pop the current node off the stack of open elements.

Acknowledge the token's self-closing flag, if it is set.

An end tag whose tag name is "colgroup"

If the current node is the root html element, then this is a parse error; ignore the token. (fragment case)

Otherwise, pop the current node (which will be a colgroup element) from the stack of open elements. Switch the insertion mode to "in table".

An end tag whose tag name is "col"

Parse error. Ignore the token.

An end-of-file token

If the current node is the root html element, then stop parsing. (fragment case)

Otherwise, act as described in the "anything else" entry below.

Anything else

Act as if an end tag with the tag name "colgroup" had been seen, and then, if that token wasn't ignored, reprocess the current token.

The fake end tag token here can only be ignored in the fragment case.

8.2.5.16 The "in table body" insertion mode

Status: Last call for comments

When the insertion mode is "in table body", tokens must be handled as follows:

A start tag whose tag name is "tr"

Clear the stack back to a table body context. (See below.)

Insert an HTML element for the token, then switch the insertion mode to "in row".

A start tag whose tag name is one of: "th", "td"

Parse error. Act as if a start tag with the tag name "tr" had been seen, then reprocess the current token.

An end tag whose tag name is one of: "tbody", "tfoot", "thead"

If the stack of open elements does not have an element in table scope with the same tag name as the token, this is a parse error. Ignore the token.

Otherwise:

Clear the stack back to a table body context. (See below.)

Pop the current node from the stack of open elements. Switch the insertion mode to "in table".

A start tag whose tag name is one of: "caption", "col", "colgroup", "tbody", "tfoot", "thead"

An end tag whose tag name is "table"

If the stack of open elements does not have a tbody, thead, or tfoot element in table scope, this is a parse error. Ignore the token. (fragment case)

Otherwise:

Clear the stack back to a table body context. (See below.)

Act as if an end tag with the same tag name as the current node ("tbody", "tfoot", or "thead") had been seen, then reprocess the current token.

An end tag whose tag name is one of: "body", "caption", "col", "colgroup", "html", "td", "th", "tr"

Parse error. Ignore the token.

Anything else

Process the token using the rules for the "in table" insertion mode.

When the steps above require the UA to clear the stack back to a table body context, it means that the UA must, while the current node is not a tbody, tfoot, thead, or html element, pop elements from the stack of open elements.

The current node being an html element after this process is a fragment case.

8.2.5.17 The "in row" insertion mode

Status: Last call for comments

When the insertion mode is "in row", tokens must be handled as follows:

A start tag whose tag name is one of: "th", "td"

Clear the stack back to a table row context. (See below.)

Insert an HTML element for the token, then switch the insertion mode to "in cell".

Insert a marker at the end of the list of active formatting elements.

An end tag whose tag name is "tr"

If the stack of open elements does not have an element in table scope with the same tag name as the token, this is a parse error. Ignore the token. (fragment case)

Otherwise:

Clear the stack back to a table row context. (See below.)

Pop the current node (which will be a tr element) from the stack of open elements. Switch the insertion mode to "in table body".

A start tag whose tag name is one of: "caption", "col", "colgroup", "tbody", "tfoot", "thead", "tr"

An end tag whose tag name is "table"

Act as if an end tag with the tag name "tr" had been seen, then, if that token wasn't ignored, reprocess the current token.

The fake end tag token here can only be ignored in the fragment case.

An end tag whose tag name is one of: "tbody", "tfoot", "thead"

If the stack of open elements does not have an element in table scope with the same tag name as the token, this is a parse error. Ignore the token.

Otherwise, act as if an end tag with the tag name "tr" had been seen, then reprocess the current token.

An end tag whose tag name is one of: "body", "caption", "col", "colgroup", "html", "td", "th"

Parse error. Ignore the token.

Anything else

Process the token using the rules for the "in table" insertion mode.

When the steps above require the UA to clear the stack back to a table row context, it means that the UA must, while the current node is not a tr element or an html element, pop elements from the stack of open elements.

The current node being an html element after this process is a fragment case.

8.2.5.18 The "in cell" insertion mode

Status: Last call for comments

When the insertion mode is "in cell", tokens must be handled as follows:

An end tag whose tag name is one of: "td", "th"

If the stack of open elements does not have an element in table scope with the same tag name as that of the token, then this is a parse error and the token must be ignored.

Otherwise:

Now, if the current node is not an element with the same tag name as the token, then this is a parse error.

Pop elements from the stack of open elements stack until an element with the same tag name as the token has been popped from the stack.

Clear the list of active formatting elements up to the last marker.

Switch the insertion mode to "in row". (The current node will be a tr element at this point.)

A start tag whose tag name is one of: "caption", "col", "colgroup", "tbody", "td", "tfoot", "th", "thead", "tr"

If the stack of open elements does not have a td or th element in table scope, then this is a parse error; ignore the token. (fragment case)

Otherwise, close the cell (see below) and reprocess the current token.

An end tag whose tag name is one of: "body", "caption", "col", "colgroup", "html"

Parse error. Ignore the token.

An end tag whose tag name is one of: "table", "tbody", "tfoot", "thead", "tr"

If the stack of open elements does not have an element in table scope with the same tag name as that of the token (which can only happen for "tbody", "tfoot" and "thead", or, in the fragment case), then this is a parse error and the token must be ignored.

Otherwise, close the cell (see below) and reprocess the current token.

Anything else

Process the token using the rules for the "in body" insertion mode.

Where the steps above say to close the cell, they mean to run the following algorithm:

If the stack of open elements has a td element in table scope, then act as if an end tag token with the tag name "td" had been seen.
Otherwise, the stack of open elements will have a th element in table scope; act as if an end tag token with the tag name "th" had been seen.

The stack of open elements cannot have both a td and a th element in table scope at the same time, nor can it have neither when the insertion mode is "in cell".

8.2.5.19 The "in select" insertion mode

Status: Last call for comments

When the insertion mode is "in select", tokens must be handled as follows:

A character token

Insert the token's character into the current node.

A comment token

Append a Comment node to the current node with the data attribute set to the data given in the comment token.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is "html"

Process the token using the rules for the "in body" insertion mode.

A start tag whose tag name is "option"

If the current node is an option element, act as if an end tag with the tag name "option" had been seen.

Insert an HTML element for the token.

A start tag whose tag name is "optgroup"

If the current node is an option element, act as if an end tag with the tag name "option" had been seen.

If the current node is an optgroup element, act as if an end tag with the tag name "optgroup" had been seen.

Insert an HTML element for the token.

An end tag whose tag name is "optgroup"

First, if the current node is an option element, and the node immediately before it in the stack of open elements is an optgroup element, then act as if an end tag with the tag name "option" had been seen.

If the current node is an optgroup element, then pop that node from the stack of open elements. Otherwise, this is a parse error; ignore the token.

An end tag whose tag name is "option"

If the current node is an option element, then pop that node from the stack of open elements. Otherwise, this is a parse error; ignore the token.

An end tag whose tag name is "select"

If the stack of open elements does not have an element in table scope with the same tag name as the token, this is a parse error. Ignore the token. (fragment case)

Otherwise:

Pop elements from the stack of open elements until a select element has been popped from the stack.

Reset the insertion mode appropriately.

A start tag whose tag name is "select"

Parse error. Act as if the token had been an end tag with the tag name "select" instead.

A start tag whose tag name is one of: "input", "keygen", "textarea"

If the stack of open elements does not have a select element in table scope, ignore the token. (fragment case)

Otherwise, act as if an end tag with the tag name "select" had been seen, and reprocess the token.

A start tag token whose tag name is "script"

Process the token using the rules for the "in head" insertion mode.

An end-of-file token

If the current node is not the root html element, then this is a parse error.

It can only be the current node in the fragment case.

Anything else

Parse error. Ignore the token.

8.2.5.20 The "in select in table" insertion mode

Status: Last call for comments

When the insertion mode is "in select in table", tokens must be handled as follows:

A start tag whose tag name is one of: "caption", "table", "tbody", "tfoot", "thead", "tr", "td", "th"

Parse error. Act as if an end tag with the tag name "select" had been seen, and reprocess the token.

An end tag whose tag name is one of: "caption", "table", "tbody", "tfoot", "thead", "tr", "td", "th"

If the stack of open elements has an element in table scope with the same tag name as that of the token, then act as if an end tag with the tag name "select" had been seen, and reprocess the token. Otherwise, ignore the token.

Anything else

Process the token using the rules for the "in select" insertion mode.

8.2.5.21 The "in foreign content" insertion mode

Status: Last call for comments

When the insertion mode is "in foreign content", tokens must be handled as follows:

A character token

Insert the token's character into the current node.

If the token is not one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), or U+0020 SPACE, then set the frameset-ok flag to "not ok".

A comment token

Append a Comment node to the current node with the data attribute set to the data given in the comment token.

A DOCTYPE token

Parse error. Ignore the token.

An end tag whose tag name is "script", if the current node is a script element in the SVG namespace.

Pop the current node off the stack of open elements.

Let the old insertion point have the same value as the current insertion point. Let the insertion point be just before the next input character.

Increment the parser's script nesting level by one. Set the parser pause flag to true.

Process the script element according to the SVG rules, if the user agent supports SVG. [SVG]

Even if this causes new characters to be inserted into the tokenizer, the parser will not be executed reentrantly, since the parser pause flag is true.

Decrement the parser's script nesting level by one. If the parser's script nesting level is zero, then set the parser pause flag to false.

Let the insertion point have the value of the old insertion point. (In other words, restore the insertion point to its previous value. This value might be the "undefined" value.)

An end tag, if the current node is not an element in the HTML namespace.

Run these steps:

Initialize node to be the current node (the bottommost node of the stack).
If node is not an element with the same tag name as the token, then this is a parse error.
Loop: If node has the same tag name as the token, pop elements from the stack of open elements until node has been popped from the stack, and then abort these steps.
Set node to the previous entry in the stack of open elements.
If node is an element in the HTML namespace, process the token using the rules for the secondary insertion mode. If, after doing so, the insertion mode is still "in foreign content", but there is no element in scope that has a namespace other than the HTML namespace, switch the insertion mode to the secondary insertion mode.
Return to the step labeled loop.

A start tag whose tag name is neither "mglyph" nor "malignmark", if the current node is an mi element in the MathML namespace.

A start tag whose tag name is neither "mglyph" nor "malignmark", if the current node is an mo element in the MathML namespace.

A start tag whose tag name is neither "mglyph" nor "malignmark", if the current node is an mn element in the MathML namespace.

A start tag whose tag name is neither "mglyph" nor "malignmark", if the current node is an ms element in the MathML namespace.

A start tag whose tag name is neither "mglyph" nor "malignmark", if the current node is an mtext element in the MathML namespace.

A start tag whose tag name is "svg", if the current node is an annotation-xml element in the MathML namespace.

A start tag, if the current node is a foreignObject element in the SVG namespace.

A start tag, if the current node is a desc element in the SVG namespace.

A start tag, if the current node is a title element in the SVG namespace.

A start tag, if the current node is an element in the HTML namespace.

Any other end tag

Process the token using the rules for the secondary insertion mode.

If, after doing so, the insertion mode is still "in foreign content", but there is no element in scope that has a namespace other than the HTML namespace, switch the insertion mode to the secondary insertion mode.

A start tag whose tag name is one of: "b", "big", "blockquote", "body", "br", "center", "code", "dd", "div", "dl", "dt", "em", "embed", "h1", "h2", "h3", "h4", "h5", "h6", "head", "hr", "i", "img", "li", "listing", "menu", "meta", "nobr", "ol", "p", "pre", "ruby", "s", "small", "span", "strong", "strike", "sub", "sup", "table", "tt", "u", "ul", "var"

A start tag whose tag name is "font", if the token has any attributes named "color", "face", or "size"

An end-of-file token

Pop elements from the stack of open elements until either a math element or an svg element has been popped from the stack, and reprocess the token.

Any other start tag

If the current node is an element in the MathML namespace, adjust MathML attributes for the token. (This fixes the case of MathML attributes that are not all lowercase.)

If the current node is an element in the SVG namespace, and the token's tag name is one of the ones in the first column of the following table, change the tag name to the name given in the corresponding cell in the second column. (This fixes the case of SVG elements that are not all lowercase.)

Tag name	Element name
`altglyph`	`altGlyph`
`altglyphdef`	`altGlyphDef`
`altglyphitem`	`altGlyphItem`
`animatecolor`	`animateColor`
`animatemotion`	`animateMotion`
`animatetransform`	`animateTransform`
`clippath`	`clipPath`
`feblend`	`feBlend`
`fecolormatrix`	`feColorMatrix`
`fecomponenttransfer`	`feComponentTransfer`
`fecomposite`	`feComposite`
`feconvolvematrix`	`feConvolveMatrix`
`fediffuselighting`	`feDiffuseLighting`
`fedisplacementmap`	`feDisplacementMap`
`fedistantlight`	`feDistantLight`
`feflood`	`feFlood`
`fefunca`	`feFuncA`
`fefuncb`	`feFuncB`
`fefuncg`	`feFuncG`
`fefuncr`	`feFuncR`
`fegaussianblur`	`feGaussianBlur`
`feimage`	`feImage`
`femerge`	`feMerge`
`femergenode`	`feMergeNode`
`femorphology`	`feMorphology`
`feoffset`	`feOffset`
`fepointlight`	`fePointLight`
`fespecularlighting`	`feSpecularLighting`
`fespotlight`	`feSpotLight`
`fetile`	`feTile`
`feturbulence`	`feTurbulence`
`foreignobject`	`foreignObject`
`glyphref`	`glyphRef`
`lineargradient`	`linearGradient`
`radialgradient`	`radialGradient`
`textpath`	`textPath`

If the current node is an element in the SVG namespace, adjust SVG attributes for the token. (This fixes the case of SVG attributes that are not all lowercase.)

Adjust foreign attributes for the token. (This fixes the use of namespaced attributes, in particular XLink in SVG.)

Insert a foreign element for the token, in the same namespace as the current node.

If the token has its self-closing flag set, pop the current node off the stack of open elements and acknowledge the token's self-closing flag.

8.2.5.22 The "after body" insertion mode

Status: Last call for comments

When the insertion mode is "after body", tokens must be handled as follows:

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), or U+0020 SPACE

Process the token using the rules for the "in body" insertion mode.

A comment token

Append a Comment node to the first element in the stack of open elements (the html element), with the data attribute set to the data given in the comment token.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is "html"

Process the token using the rules for the "in body" insertion mode.

An end tag whose tag name is "html"

If the parser was originally created as part of the HTML fragment parsing algorithm, this is a parse error; ignore the token. (fragment case)

Otherwise, switch the insertion mode to "after after body".

An end-of-file token

Anything else

Parse error. Switch the insertion mode to "in body" and reprocess the token.

8.2.5.23 The "in frameset" insertion mode

Status: Last call for comments

When the insertion mode is "in frameset", tokens must be handled as follows:

A character token that is one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), or U+0020 SPACE

A comment token

Append a Comment node to the current node with the data attribute set to the data given in the comment token.

A DOCTYPE token

Parse error. Ignore the token.

A start tag whose tag name is "html"

Process the token using the rules for the "in body" insertion mode.

A start tag whose tag name is "frameset"

Insert an HTML element for the token.

An end tag whose tag name is "frameset"

If the current node is the root html element, then this is a parse error; ignore the token. (fragment case)

Otherwise, pop the current node from the stack of open elements.

If the parser was not originally created as part of the HTML fragment parsing algorithm (fragment case), and the current node is no longer a frameset element, then switch the insertion mode to "after frameset".

A start tag whose tag name is "frame"

Insert an HTML element for the token. Immediately pop the current node off the stack of open elements.

Acknowledge the token's self-closing flag, if it is set.

A start tag whose tag name is "noframes"

Process the token using the rules for the "in head" insertion mode.

An end-of-file token

If the current node is not the root html element, then this is a parse error.

It can only be the current node in the fragment case.