FB Gamer will automatically/magically resize the games to the browser's inner width/height, quite useful for those games which does not have full-screen mode.
One of the facts of the Games is they're inserted on the site by using iFrames (vast majority of them, at least) since FB is just a partner serving the games from other websites... The magic from this add-on is just to get those iframe's content alone, resizing it on-the-fly to the browser dimensions.
As said, most of the games uses iFrames, but not all... during development we've found a couple of games (2% or so..) which uses normal embed objects. Those specific games will not be touched by this add-on, since there are others for this purpoose.
Also note this is a WIP release, please feel free to report any non-working game to be able to fix it (IF possible within the scope of this add-on), and remember you can disable/enable the add-on at anytime by clicking the status-bar icon. (clicking the icon while on a Game page will automatically resize it, so you can play with the switch if you do not want it to work over all games)