I had used PopUp Killer before, and it had some nice features including a thing that, when a popup first came up, allowed you to select whether it's a "good" or "bad" popup. So the CNN/Comcast ones could be easily added to the "these are okay" list (or, if you're Fabris, the "go the hell away" list.) But PopUp Killer also worked by reading titles/URL's of the popups, and that's far from ideal, and often it would bring my system to a crawl as it was trying to close the popups. So I got rid of it.