Control.Tabs is a simply wonderful JavaScript extension for the Prototype library. In one project I'm using in multiple places and it fits the requirements perfectly. There is, however, a weird problem with one page with IE where instead of displaying the form like this:

<cut>

I've posted this with a solution on my employer's blog:
http://rorblog.techcfl.com/2007/11/18/weird-problem-with-controltabs-and-ie67-solved/