Reorganized and further clarified security considerations regarding malicious objects, phishing, and presence leaks.
Reorganized and further clarified security considerations regarding malicious objects, phishing, and presence leaks; added business rule about inclusion and processing of hyperlinks.
The use of structural elements is NOT RECOMMENDED where presentational styles are desired, which is why very few structural elements are specified herein. Implementations SHOULD use appropriate 'style' attributes (e.g., <span style='font-weight: bold'>this is bold</span> and <p style='margin-left: 5%'>this is indented</p>) rather than XHTML structural elements (e.g., <strong/> and <blockquote/>) wherever possible.
Nesting of block structural elements (<p/>) and list elements (<dl/>, <ol/>, <ul/>) is NOT RECOMMENDED, except within <div/> elements.
It is RECOMMENDED for implementations to replace line breaks with the <br/> element and to replace significant whitepace with the appropriate number of non-breaking spaces (via the NO-BREAK SPACE character or its equivalent), where "significant whitespace" means whitespace that makes some material difference (e.g., one or more spaces at the beginning of a line or more than one space anywhere else within a line), not "normal" whitespace separating words or punctuation.
When rendering XHTML-IM content, a user agent SHOULD NOT render as a hyperlink text that is not structured via the <a/> element from the Hypertext Module; therefore if the sender wishes text to be linked, the sending user agent MUST represent the text using the <a/> element and appropriate attributes.