When installing Ubuntu on one of the new machines we get from time to time, there's a common mechanism I repeat over and over with Firefox:
      - install the Firebug extension
 - install the Web Developer extension
 - install the ShowIP extension
 - install the GooglePreview extension
 - change the link of the start bar icon to start Firefox, to "firefox -no-remote -ProfileManager %u" instead of "firefox %u"