Last days I'm developing few XHTML 1.0 Strict web pages. Why XHTML? Easy, HTML has been a wide use language to write web pages, w3c recomends to use XML, and promote browsers to support this specification.

In that scenario, XHTML offers more than HTML but an easy aproach to XML. If you're use to write HTML you may learn XHTML fairly well, then, when you webs applications becomes bigger you may migrate to XML environment, where pages are generated on the fly by parsing pure XML documents via XSLT (wich is a template for that) in XHTML or HTML...

Again, I'm come from webmaster tasks, not from development, if you wanna know more visit http://www.w3.org/MarkUp
NOTE I'm considering to writte an article about this basis...