Here's a sample of the source code from the link you provided:
<LINK rel="stylesheet" href="/css/search.css" type="text/css">
<link rel="stylesheet" href="/seo.css" type="text/css">
<link rel="stylesheet" href="/css/networkbar.css" type="text/css">
<link rel="stylesheet" href="/style.css" type="text/css">
<link rel="icon" href="/favicon.ico" type="image/x-icon">
<link rel="shortcut icon" href="/favicon.ico" type="image/x-icon">
<SCRIPT src="/js/alt.js" language="JavaScript" type="text/javascript"></SCRIPT>
<SCRIPT src="/js/common.js" language="JavaScript" type="text/javascript"></SCRIPT>
<SCRIPT src="/js/dynwindow.js" language="JavaScript" type="text/javascript"></SCRIPT>
<script src="/js/networkbar.js" language="JavaScript" type="text/javascript"></script>
<script src="/js/preview_templates.js" language="JavaScript" type="text/javascript"></script>
<script src="/js/loader.js" language="JavaScript" type="text/javascript"></script>
<script src="/js/AC_RunActiveContent.js" language="JavaScript" type="text/javascript"></script>
<SCRIPT language="javascript" type="text/javascript">
The part I highlighted in red shows how they do it. They use a javascript called preview_templates.js
You can probably find that script in a number of places. I usually recommend
http://javascriptsource.com mostly because it's the only url I can remember off the top of my head.