image roll over

If you have Firefox with the developers toolbar you can view the javascript that is being executed. That should give you an idea of how it works.

OK, so I need to break out the Javascript book. I am currious to know how or why they load so fast. Very cool script. Well off to a JavaScript forum as well.
Thanks

I don't think that involves Flash or Java, actually. It looks like a JavaScript function. Each thumbnail has code like this:

onmouseover="showtrail(' http://www1.istockphoto.com/file_thumbview_approve/2409748/2/istockphoto_2409748_jet.jpg','Jet','A commercial airliner prepares to land.','5.0000','1','1',253,1);" onmouseout="hidetrail();"

which refer to JavaScript functions showtrail and hidetrail. Those functions are probably contained in one of the JavaScript files loaded in the head of the HTML document:
<script language="javascript" src="/js/scriptaculous/prototype.js" type="text/javascript"></script>
<script language="javascript" src="/js/utility.js" type="text/javascript"></script>
<script language="javascript" src="/js/search.js" type="text/javascript"></script>
<script language="javascript" src="/js/styleswitcher.js" type="text/javascript"></script>
<script language="javascript" src="/js/dom.js" type="text/javascript"></script>
<script language="javascript" src="/js/sifr.js" type="text/javascript"></script>
<script language="javascript" src="/js/popupbox.js" type="text/javascript"></script>
<script language="javascript" src="/js/filesearchhover.js" type="text/javascript"></script>
<script language="javascript" src="/js/copyspace.js" type="text/javascript"></script>
<script language="javascript" src="/js/lightbox.js" type="text/javascript"></script>