I found a site that tests your web browser’s security, trying various exploits to see if you’re vulnerable to them.
There’s another site that tests you how well your browser blocks popups.
Occasionally I’ll get a popup, but it’s been so infrequent that I haven’t bothered figuring out how they’re getting through.
I’ve found Firefox’s built in blocker to let in a few every now and then, but I really like Opera’s built in blocker. I set it so that it blocks every and all popup(s).