I have Vista and use Firefox. I've been bothered by pop unders. I don't understand why Firefox doesn't block them automatically, you close out the window you are looking at and there they are. Sometimes several stacked on top of each other. Anyway I DOWNLOADED the RECOMMEND Firefox add on. I copied the address of the most persistent pop unders (Netflix and Billpay) and put them in the filter option. It doesn't work! Is there anything that would work? Thank you.In Firefox go to the main menu and look under - Tools - Options - Content : Is the box "block popup windows" un-checked? Make sure that is checked and see if you still have the problem. You might want to restart Firefox also.Do what dude1234 says and it should eliminate most, but not necessarily all, of the pop unders, but there are some sites where they have figured out a way to get around pop under, or over, blockers.

There is one site I go to several times a week, and no MATTER what I do they always seem to get a pop under through. As long as web sites make their money through advertising, that's always going to be a problem. You can MINIMIZE it, but it's NEVER going to completely go away.