You only have to save it as a .html-file and not under a special file name.
The biggest difference between HTML and XHTML is:
1) That XHTML is more case-sensitive and only want small letters.
I.E: <p> instead of <P>
2) <br> has turned into <br />
3) XHTML is very distinct about the order of "nestled"-tags,
which means FILO (first-in-last-out)
I.E: <div> <i> <strong>some text</strong> </i> </div>
instead of what was incorrectly accepted as OK in HTML:
<div><i><strong> some text </i></strong></div>
4) And the mandatory XHTML-file should at least contain this:
- <!DOCTYPE Doctype goes here>
-
<html xmlns="http://www.w3.org/1999/xhtml">
-
<head>
-
<title>Some title</title>
-
</head>
-
<body></body>
-
</html>
Hope this was of some help, there's an simple introduction tutorial at w3schools:
http://www.w3schools.com/xhtml/default.asp
//Paks