ok so typically there are these DHTML popup windows now days.
Some trigger when the mouse leaves the "viewing area" and mowes to the functional top protion of the browser. This first triggers a DHTML popup with in the content fo your website that is typically unblockable.
Then Second after this threshold line has been crossed a clause is create so that when the user CLICKS (at all) a [url removed, login to view] window is created, that should be unblockable because it was called into exsistance via this triggered click in the specified space.
---- If i can duplicate this you stand to earn $300 ----