Back/Forward Gestures do not work in Mac OS X Lion
Safari uses one-finger gestures with lion to support back/forward browser buttons Need firefox upgrade to do the same, because mission control intercepts the previous gestures.
This is probably the wrong place to ask for changes and feature requests.
A small little workaround to achieving something SIMILAR to Safari's natural back/forward gestures in Firefox is to switch two values: browser.gesture.swipe.left and browser.gesture.swipe.right
For browser.gesture.swipe.left, change its value to Browser:ForwardOrForwardDuplicate
For browser.gesture.swipe.right, change its value to Browser:BackOrBackDuplicate
Now when you swipe like you do in Safari to go back/forward to whatever page you want to view, you will do the same in Firefox just without the cool GUI implemented by Safari.
I just downloaded Firefox Beta 9.0b5 and this issue is fixed. I can navigate with my Magic Mouse with only one finger swipe. I'm so glad that this issue is finally fixed. :)
Here is the workaround I'm using, switch to Chrome which has had this feature within a couple weeks of Lion being released. Why would you stick with this memory hog with the never ending appetite for RAM?
Using Chrome is not a solution for Firefox. I use firefox for many of its features, especially the bookmark keywords you can make. Also its widely compatible with many web sites including financial institutions. I use two finger swipes to go back and forward on web pages, which perfectly works fine with firefox.