That’s why, I guess, I’m none too engaged by the wailing and gnashing of teeth around the current HTML5/XHTML2 conversation taking place across the web at the moment. Because whatever flavour of mark-up you use, you should always do those two things and there are still a ton of developers who don’t.
I switched from HTML4 to XHTML some time ago because I felt it gave me the structure I wanted in my coding. It was virtually always served using a
text/html MIME type so it was pretty much HTML4, but with XML syntax. It just seemed cleaner and more structured and helped hone my trade.
There are still very few websites out there that are using XHTML properly (with an
application/xhtml+xml MIME type) compared to the thousands of sites created by WYSIWYG tools that are barely proper HTML, let alone semantic or validated. I would rather concentrate on cleaning those up and educating developers to code sematically and validate their code correctly going forward, before lameting XHTML2, which seemed on a hiding to nowhere from the get go.
The next freelance web site I build will probably be in HTML4, just to brush up. All subsequent ones will be HTML5.