about:config
Type dom in the filter bar.
You can control what is and isn't allowed to be set, changed or disabled by popups and so on. Set the value to True to disable the feature.
Very handy not just to stop popups disabling the address bar, but to make every popup resizeable, have a scroll bar, and generally behave properly.
Don't set dom.disable_image_src_set to true, or you will have problems with a lot of images, including avatars on forums.
Hope this helps.
