Inert Gas Design
(XHTML Document)

A bare minimum XHTML document must include:

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
 <head>
  <title></title>
 </head>
 <body>
  <p></p>
 </body>
</html>

What's left is to add a title, and fill in the body. The body show above has an empty paragraph in it, as an empty body is not permitted. There should really be no empty tags, if a tag is used, it should have some non-empty contents, but an empty title or paragraph is valid, where an empty head or body isn't.

Contents:

Valid XHTML 1.1!
Valid CSS!