A family of
XML markup languages that mirror or extend versions of the widely used Hypertext Markup Language (
HTML).
XHTML 1.0 became a
W3C Recommendation on January 26, 2000.
XHTML 1.1 became a
W3C Recommendation on May 31, 2001. XHTML5 is undergoing development as of September 2009, as part of the HTML5 specification.