[support] Which module would create jQuery splash page?

[crozilla]

I was wondering how to create a situation whereby a first-time visitor 
would see the website overlayed by a "jQuery/Lightbox-esque" modal 
window warning them that the site contains adult language, and that they 
could then click "I understand" or something to make it go away.

I don't want to use a separate page to do this (ala, the 'Front Page' 
module).

Any ideas? Thanks in advance.

Peter