Each Guideline and each Technique has a priority listed. For the guidelines, the priority refers to the importance of addressing the issue identified by the guideline. For Techniques, there may be a number of techniques used to improve accessibility with respect to this guideline. For example a priority 1 Guideline may have a priority 1 Technique, which MUST be done to provide accessibility, and a priority 3 Technique, which MAY also be done to help address the issue.
Provide alternative representations of all non-text information so that a page may be perceived and used without being seen and without being heard. | |||
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Guideline | Rationale | Techniques | |
1. | Provide alternative text for all images, applets, and image maps, including images used as submit buttons and all of the links within a client-side image map. [Priority 1] | Otherwise, users
who are blind, have low vision, or
have chosen not to view graphics will not know the
purpose of the visual components on the page.
Example Since ASCII art uses characteres to create a visual image there is no way to attach alt-text as with other images. |
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2. | Provide descriptions for graphics, scripts, or applets that convey important information. [Priority 1] | Otherwise, important information presented graphically (charts, billboards, diagrams) will not be perceivable to people with blindness, some people with low vision, and users who have chosen not to view graphics, scripts, or applets or whose browser does not support scripts or applets. |
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3. | Provide textual equivalents (captions) of all audio information. If the audio is associated with a visual presentation (movie or animation), synchronize the textual equivalents with the visual presentation. [Priority 1] | Otherwise, users who are deaf, or hard of hearing, or who have turned sound off cannot perceive the information presented through sounds such as speech, sound effects, and music. |
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4. | Provide auditory descriptions of moving visual information (movies, animations, etc.). If the visual presentation is associated with an auditory presentation, synchronize the auditory descriptions with the existing auditory presentation and collate the text version of the descriptions with the text transcript (captions) of the primary audio track. [Priority 1] | Otherwise, users who cannot see (or look at) the page will not be able to perceive information presented through action, body language, or other visual cues that are not available through the auditory information (dialogue, sound effects, etc.). |
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5. | Use structures that support the inclusion of alternate presentation types. [Priority 1] | If other types of information, such as images, are used as the source of a frame there is no way to attach alternative information to the information. In the image example, there is no way to attach alt-text (.see A-1). | The source of a frame should be an HTML file. [Priority 1] |
6. | Avoid use of color in a way that causes problems for people with color blindness. [Priority 1] | If color is used to convey information, be sure information is perceivable to those who can not perceive color. (guideline or strategy??) contrast and coding. needs work |
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Enable the document to be presented in a
variety of media types with a variety of output devices.
OR Enable the document to be reformatted for the purpose of presentation in different media and different output devices. |
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Guideline | Rationale | Techniques | |
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1. | Separate content and structure from presentation. [Priority 2] | When content is
tied to presentation, such as color-coding list items to distinguish
between them in some way, it is difficult to impossible to transform the
information into a different modality.
Example. Character spacing and non-letter characters cause problems for screen readers. |
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2. | Use elements and attributes appropriately. [Priority 2] | When elements and attributes are used inappropriately, such as using structural elements for presentation purposes (e.g., H1 to create large, bold face text), user agents that allow users to navigate through the structure will be unable to do so properly. Reformatting the page for other media and devices can also be difficult. |
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3. | Ensure that moving, blinking, scrolling, or auto-updating objects or pages may be paused or frozen. This is particularly important for objects that contain text. Note. Does not apply to instant redirection. [Priority 1] | Some people with
cognitive limitations or visual disabilities
are unable to read moving text quickly enough or at all. Movement can
also cause such a distraction that the rest of the page becomes
unreadable for people with cognitive disabilities. Screen readers are
unable to read moving text. People with physical disabilities
might not be able to move quickly or accurately enough to interact with
moving objects. Photo epilepsy?? |
Note. Avoid BLINK and MARQUEE since they are proprietary elements. |
4. | Changes in language within text should be identified. (Need for any text to identify clearly the language that it is written in.) [Priority 2] | This is a particular problem for Braille translators, especially when multiple languages appear on the same page. | Use the "lang" attribute to identify the language of the text. [Priority 2] |
Ensure all elements on a page are operational in a device independent fashion. | |||
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Guideline | Rationale | Techniques | |
1. | Ensure that pages using newer technologies will fail gracefully if the technology is not supported or is turned off. [Priority 1] | With each release of HTML new features have been added. Older browsers ignore new features and some users configure their browser not to make use of new features. These users often see nothing more than a blank page or an unreadable page when new technologies do not fail gracefully. | New technologies
must fail gracefully and accessibly. [Priority 1]
See also E-5 - text-only pages. |
2. | Enable keyboard operation of all page elements. [Priority 1] | Someone who is using the page without sight, with voice input, or with a keyboard (or other input device other than a mouse) will have a difficult time navigating a page if keyboard shortcuts are not provided for objects on the page. Access to image maps is impossible for these users if alternatives are not provided. |
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3. | Provide interim solutions to facilitate operation via assistive technologies and older browsers. [Priority 2] | Older
browsers are unable to "Tab" to edit boxes, text
areas and lists of consecutive links, making it difficult to impossible
for users to access them. Users not operating in a graphical environment are disoriented by being transferred to a new window without warning. |
Until most users
are able to secure newer technologies that address these issues:
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Provide meta-information for complex elements as orientation and contextual cues. | |||
Guideline | Rationale | Techniques | |
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1. | For frames, provide sufficient information to determine the purpose of the frames and how they relate to each other. [Priority 1] | Users with
blindness and low vision often
access the screen with "tunnel vision" and are unable to get
an overview understanding of the page. Complex intertwinings of frames
may also be difficult for people with cognitive disabilities
to use.
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2. | Properly markup abbreviations and acronyms. [Priority 2] |
Unless expansions for abbreviations and acronyms are provided they may be indecipherable when spoken or brailled. |
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3. | Group controls, selections, and labels into semantic units. [Priority 2] | Groupings provide meta-information about relationships between controls that are useful for all users. |
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4. | Ensure that tables have necessary markup to be properly restructured or presented by accessible browsers and other user agents. [Priority 1] |
Many user agents restructure tables to present them. Without appropriate markup the tables will not make sense when restructured. Tables also present special problems to users of screen-readers. These guidelines benefit users that are accesing the table auditorally or viewing only a portion of the page at a time (users with blindness and low vision, or using an auto-pc, or devices with small displays) |
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5. | Create link phrases that make sense when read out of context, but that are not too verbose. [Priority 3] | Users that access a page auditorally (users with blindness, low vision, or those using an auto-pc) often tab through the links on a page. If a link does not make sense when read out of context, they will have to stop to read around the link to gather the context. | Create link phrasesthat make sense when read out of context that are not too verbose. [Priority 3] |
General | |||
Guideline | Rationale | Techniques | |
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1. | Use elements, attributes, and style rules that comply with one of the W3C HTML or CSS specifications. [Priority 1] | By avoiding proprietary elements and complying with a W3C specification you increase the likelihood that your page will be more consistent across platforms as well as more usable by a variety of populations. | Use a "W3C
validator" to check pages such as the
HTML Validator Service
[Priority 1].
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2. | Objects or elements that contain their own user interface should have accessibility built in. | The accessibility of objects with their own interface is independent of the accessibility of the user agent. Accessibility must therefore be built into the objects. |
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3. | Ensure that there are accessible alternatives to information or functionality provided by active content such as scripts and applets. [Priority 1] | Many users can not run scripts or applets at all. The "fail gracefully" provisions would cover this situation. However, some users who can, but rely on assistive technology such as screen readers or special input devices may not be able to receive the information, or activate the functions that the content provides. |
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4. | If, after best efforts, any page is still not accessible, provide a link to an alternative page that is accessible, has equivalent information, and is updated as often as the inaccessible page. [Priority 1] | Some pages will
be unable to fail gracefully at this time either because the visual
components are too complex, or because assistive technologies or user
agents (browsers) are lacking a specific feature. Known instances when a text-only page will be needed (not a definitive list):
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If you can not
make a page accessible then do one of the following [Priority 1]:
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