[support] Which module would create jQuery splash page?

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