V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

XHTML
       eXtended HyperText Markup Language (HTML, WWW, XML)


The Free On-line Dictionary of Computing (30 December 2018):

Extensible HyperText Markup Language
XHTML

    (XHTML) A reformulation
   of HTML 4.01 in XML.  Being XML means that XHTML can be
   viewed, edited, and validated with standard XML tools.  At the
   same time, it operates as well as or better than HTML 4 in
   existing HTML 4 conforming user agents.

   The most important change is that all elements must be
   terminated, either with a closing tag or using the 
   shorthand.  So, instead of

   	

   you would write

   	

   The space before the "/" is required by some older browsers.
   Other differences are that tag and attribute names should be
   lower case and all attributes should be quoted.

   XHTML Home (http://w3.org/TR/xhtml1/).

   Quick Summary
   (http://technorealm.co.uk/design/html-to-xhtml-conversions.html)

   (2006-01-19)