The Opera browser comes with a popup killer built-in.
GO ON - YOU CAN ALL YAWN IF YOU WANT TO - I DON'T MIND.
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I use Popup Cop when I'm forced to use Internet Explorer. It has a built-in Cookie Manager, plus loads of other tweaks, and will warn you if a site is trying to download anything to your PC. It has to be registered after a trial period, but if I type the words "Google Groups", I'm sure you'll know what I mean!