my guess would be a combination of:
css for style
dhtml to get the tabs
webobjects for the dynamic aspects of the links [keep in mind that the dynamic stuff could be done with a variety of technologies, like PHP, ASP, JSP, PSP, and more.]
I'm basing this guess off of visually glancing at the web page. I haven't yet looked at the source code. (too much going on at work for me to spend another 5 minutes. hopefully my 'guess' will point you in the right direction to learn more about how it's done)
good luck.