It's javascript. Google "javascript full screen" for lots of scripts. Here's one:-
http://javascript.internet.com/navig...ll-screen.html
I think it's a very old script because it begins with <SCRIPT LANGUAGE="JavaScript"> when it should be <script type="text/javascript">
Many people don't like their browser controlled in this way and experts say you shouldn't do it.
Code downloaded to my PC will be deleted in due course.
WIN7; IE9, Firefox, Opera, Chrome and Safari for Windows; screen resolution usually 1366*768.
Also IE6 on W98 with 800*600 and IE8 on Vista 1440*900.