XHTML 1.0 became an official W3C Recommendation January 26, 2000.
A W3C Recommendation means that the specification is stable, that it has been reviewed by the W3C membership, and that the specification is now a Web standard.
Today's market consists of different browser technologies, some browsers run internet on computers, and some browsers run internet on mobile phones and hand helds. The last-mentioned do not have the resources or power to interpret a "bad" markup language.
By combining HTML and XML, and their strengths, we got a markup language that is useful now and in the future - XHTML.
XHTML pages can be read by all XML enabled devices AND while waiting for the rest of the world to upgrade to XML supported browsers, XHTML gives you the opportunity to write "well-formed" documents now, that work in all browsers and that are backward browser compatible !!!