Sometimes there are better friends than Google and this time the friend is common sense (and the web developer toolbar): View the source code, find the elements that mark up the navigation in question. The navigation items have a class called “headlink”. A quick search (Ctrl+F/Cmd+F) for “headlink” in the JavaScript files reveals that the function is written/executed in
http://dojocampus.org/explorer/featu...ureexplorer.js Obviously this is a JavaScript framework (as I have suspected already – alough I didn’t know that one yet) and a quick search for “addonload” (since that function name was unfamiliar to me) brought me to
http://dojotoolkit.org/ where you have everything you need to create that very effect.
On a side note: the Dojo toolkit isn’t the only one that can do this. Mootools et al have similar functions (easeIn, easeOut etc.).