. XHTML
XHTML is an $XML compatible version of $HTML
that was promulgated by the $W3C on the 26th of January 2000.
Here is a link to a sample page  using $XHTML:
.See http://www/dick/samples/sample.xhtml
Use this to test your browser.

The specification is at
.See http://www.w3.org/TR/2000/REC-xhtml1-20000126/

The W3 Consortiuum support the Web and provide
.See http://w3schools.com/
as a family of tools for learning the technology.

If I understand XML correctly the main changes will be that
.List
 (1) All tags will have lower-case identifiers,
 (2) There will be no optional omitting of end tags from
certain structures like `<p>` and `<br>`, 
 (3)`Endless` tags will have the XML format `<img ...../>` or `<br></br>`.
 (4)An attribute like `ISMAP` must be written like this `ismap="ismap"`
 (5)All attribute values must be quoted.
 (6) An `id` attribute will be used instead of `name`.
.Close.List

. Glossary
HTML::=http://www/dick/samples/comp.html.syntax.html,
the HyperText Markup
Language.
XML::=http://www/dick/samples/xml.html,
the eXtensible Markup Language

W3C::=http://www.w3.org/, World Wide Web Consortium.