They are using a script from dynamic drive called Tab Content Script (v 2.0)
http://www.dynamicdrive.com/dynamici...tabcontent.htm
It's a very easy script to install and configure for use within vbulletin. I have it (as well as the AJAX Version) running on multiple sites. I just wrote a vbadvanced "how to" for the AJAX Version of this script a few days ago. Both versions are very easy to use.
btw...
They are in violation of Dynamic Drive Policies as the below comment has been removed.
Code:
/***********************************************
* Tab Content script v2.0- ? Dynamic Drive DHTML code library (www.dynamicdrive.com)
* This notice MUST stay intact for legal use
* Visit Dynamic Drive at http://www.dynamicdrive.com/ for full source code
***********************************************/