XHTML 1.0: the First Step

A reformulation of HTML 4 in XML 1.0: three DTDs are provided - Strict, Transitional, Frameset

Compatibility with existing HTML user agents is possible by following a small set of guidelines described in Appendix C

XHTML 1.0 became a Recommendation on 26 January 2000, the Second Edition will become a Recommendation soon

But XHTML 1.0 is only a part of the XHTML Family