These are things to watch out for to make sure your
data can be parsed by standard implementations.
Text Elements
nesting errors
Names
34 character max.
Normal Text Content
Use entities for all <, > and & characters.
@@@ Latin 1 characters?
comment: The sample implementation
groks. For copyrights, RCS keywords, etc.
processing instruction: If you've _got_ to
stick TeX macros or something in there, use this. The sample
implementation won't even tell you it's there, though.
Literal Text Content
Try to use as few entities as possible in Literal mode: only
treat '<' followed by '/', & followed by a letter or '#',
and > when it follows ]] as entites. Old-style clients
will display markup in an RCDATA section as data.
tags are fine!
& as long as it's not followed by a letter or '#', it's fine!
is even ok, unless it's followed by a letter or a number.
Other Elements
TITLE
Keep the title short and free of <, >, and & characters.
No newlines.
Anchors
Thou shalt quote thy URLs. Use NAMEs that start with a letter.
Remember: 34 chars max.