Well, as long as you want some pop up windows to open, it's going to be a constant battle to filter the adds vs the legitimate windows. In the beginning, the adds used onload while the legitimate windows used onclick. So, you block the onload. So then the adds start trigging them with an onclick when you click on something you want open. And so on.

Click and Run flash is a great firefox extension. You should have it weather or not flash can spawn a window. There is the occasionall all flash web site that requires clicking and running three flash items per page, but those aren't very common.

Matthew