XHTML 1.0

XHTML™ 1.0 The Extensible HyperText Markup Language (Second Edition)
A Reformulation of HTML 4 in XML 1.0
W3C Recommendation 26 January 2000, revised 1 August 2002
superseded 27 March 2018

XHTML 1.0: The Extensible HyperText Markup Language (Second Edition).