I'm assuming you're talking about the multi-touch trackpad gestures?
Well to get that to work with firefox you ahve to install the
multiclutch preference pane. Then you have to click the multiclutch link in system preferences and set the various keyboard shortcuts in firefox to work with the gestures you want. For example I set cmd+left arrow to use the swipe left gesture, which makes firefox recognize swiping left as "back"