File these under “why you should not use XHTML” - why DOCTYPES not relevant? and Sending XHTML as text/html Considered Harmful.

My conclusion - always declare the DOCTYPE from HTML 4.0 for web pages, and ignore XHTML.

Frankly using XHTML is like filing all your bills alphabetically - it sounds like a good idea, but turns out not to be worth the time invested. After digesting a series of books on HTML 4, CSS, Javascript and DOM - I just don’t see any advantage to XHTML. Sure it is “nice” that as well-formed XML it passes validation (or at least can in theory). Since web pages are in almost every case served to web browsers, and browsers have excellent HTML parsers, there is no gain there. If you want to serve XML over the web as an API to non-browser clients, there just isn’t any reason I can see to use XHTML. Sure, XHTML is a new-and-improved cleaner version of HTML. This is “nice” but not important. Sure it would be “nice” if all the HTML on the web was XHTML (as this makes writing parsers easier), but this will never happen. As long as the majority of the web is HTML you will need HTML parsers. As long as you must have HTML parsers, the XHTML parsers are simply redundant.

There is a lot of function in HTML 4, CSS, DOM and Javascript. We have only recently been able to count on near-universal HTML 4 support, and the majority of the web does not take advantage of what is already there. I think it fair to say that as a profession we are still learning to take advantage of current available function. I am a long ways from convinced that XHTML or XForms or CSS3 (or the like) is really enough of a gain to be worth the trouble.