One of the first things I do when I install Firefox is go to the advanced javascript settings and unselect "Move or resize existing windows". There are tons of pesky sites out there that resize your browser window through irritating scripts, and this keep them from doing so quite effectively.

As with all technologies though, there are occasional sites that use similar scripts for good. Some open popup windows for images and adjust their sizes to fit the content for instance. With the javascript setting I described above, this leaves me with a non-resizable popup of the wrong size. Usually a very small one with large contents.
I found today that there's also a setting you can change to keep all windows resizable. That way you can at least drag the adjust the size manually. Here's how to go about it.

  1. Type 'about:config' in the address bar to get to the configuration screen.
  2. In the search box, type 'dom.disable_window_open_feature.resizable'.
  3. This will filter the huge list of settings down to only the one you'll need to change.
  4. Right click the only line now left and select 'toggle' to set it to 'true'.