When I press "back" on my browser, it doesn't take me back. This is up there in annoyances with people stopping their car in a merge lane, websites that auto-play music, and people who speak exclusively with cliches.
Pretty awesome! Gif size goes up really quickly based on length, image size, dithering etc. So a lot of people reduce those so that their gifs are smaller and can load quickly. So maybe a full-screen treatment is not the best idea!
This should be at the top of your list of bugs.