pop out text box

Hi,
What is the best way of producing pop outs when someone clicks on the link. I
want a popout that appears on the top of the original page (with the orignal
page going dark in the background). In this case it is a text link with a page
of information popping out. A close button at the bottom that closes the page
and the original page then brightens and is usable again.

There must be a plugin for this as I see it all the time. So any advice would
be great.
Cheers

I can't beleive it. I checked my post and the post below is asking the same question. Sorry for wasting your time everybody!