I think you mean about:config, right? Setting '''dom.disable_open_during_load''' to false actually disables the popup blocker, so go ahead and reset that to the default. Or just check the box in Options > Content. If you look at '''dom.popup_allowed_events''' you will see that Firefox allows popups for certain actions it assumes are user generated. If you are finding that sites are tricking Firefox by displaying popups without a user action, you can clear this list of some or all of its items. Then in theory you should see many fewer popups. However, I haven't tested it myself.