Ok, I just posted in Z's pi Thread, and look at what came up when I hit the "Post" button:
( Click for larger [ 1024x768, 60kB ] Image )
As you can see from the image, this isn't a pop-up, or anything else like that, it is simply part of the page when it loaded.
[EDIT]
I had to scroll down ( off the bottom of the screen ) to be able to see the page ( besides the naviagation bar which you can see in the screeny ) and when I resized the page, the ad resized with it so that I only just had to scroll off the bottom of the page to see the forum.
It isn't the forum, so I take back all that I have just said, and apologise for wasting your time.
[/EDIT]
Jess.
Team EOD :: Programmer/Logical Engineer/All-Round Nice Guy