10 years later and where XHTML get us? It gave work, it gave headaches, ...
Simon Pieters researched the XML-compliance of mobile browsers and concluded
the claim that XHTML would be needed for mobile devices is simply a myth
Mobile devices are really fast and some have more processor capabilities (and even memory) than my computer had 10 years ago.
Tim Berners-Lee posted in his blog in 2006:
Some things are clearer with hindsight of several years. It is necessary to evolve HTML incrementally. The attempt to get the world to switch to XML, including quotes around attribute values and slashes in empty tags and namespaces all at once didn't work. The large HTML-generating public did not move, largely because the browsers didn't complain. Some large communities did shift and are enjoying the fruits of well-formed systems, but not all. It is important to maintain HTML incrementally, as well as continuing a transition to well-formed world, and developing more power in that world.
The plan is to charter a completely new HTML group. Unlike the previous one, this one will be chartered to do incremental improvements to HTML, as also in parallel xHTML.(...)
And now HTML5 (under development) is bringing a ton of actually useful technologies: advances in HTML forms, native video support, a vector API/canvas, Microdata,....and already major browsers are supporting part of it!
That was what I was expecting in 2000...make incremental improvements to HTML, try to show that making it HTML transitional is good (HTML transitional is and HTML that is XML complain = closing tags) but not forcing it!
One major problem was that if you have a XHTML that had some error the browser simply will not display the user cannot choose to display it even so. And sometimes that was due to some connection problem other times the problem could have being due to the editing tool not making 100% XHTML complain code or some free field value entry...And the user would simply go to another site not even seeing some info from your site. An so many bad HTML sites exists where the bad HTML is "fixed" by the browsers (maybe they are not showing exactly the same look for the site) and the client can see it well enough or even ignore that some parsing error exists (like a table row not closed).
Anyone still uses/remember WAP? Does the costs of implementation were justified?
I know some companies were WAP and XHTML migration were simply a money lost program. Trying to stay ahead of concurrency companies only changing the technology medium (only because!) but not at the same time improving the product is a killer.
Thinking that the Moore's law doesn't apply to mobile and domotics technology is a very strange notion.
Study what HTML5 can do for you to improve your communication medium, check costs/benefits and make your decision. Beware not all the HTML5 is supported right now but the main areas of it are very stable ones and the final version should only have some minor changes.