Thanks! I didn't know about that. I can't watch videos anyway, so it would be great, and might make it so I can view pages with lots of videos on them!
edit: Firefox just updated, and all those versions are currently incompatible with the new version. I hope they update it!
you can set adobe flash to 'ask to activate' - this will stop the videos from loading but not the animated gifs
just go to add-ons in ff and set your preference