What the heck are "mouse/trackpad gestures" anyway? I never used them - in fact I've never had a Mac that supported them out of the box.
mice gesture is when you can click and drag your mice within browser for a short distance toward all kinds of direction(s) to operate the browsers, such as backward, forward, open a tab, close a tab, goto home page, save page, zoom in, zoom out, etc, etc (the firegestures addon for firefox probably offers 100+ operations you can do)
from firegestures homepage
FireGestures is a Firefox extension which enables you to execute various commands with five types of mouse gestures:
* Mouse Gestures (Move mouse with holding right-click)
* Wheel Gestures (Scroll wheel with holding right-click)
* Rocker Gestures (Left-click with holding right-click and vice versa)
* Keypress Gestures (Mouse gesture with holding Ctrl / Shift key)
* Tab Wheel Gestures (Scrolling wheel on the tab bar)
that green line is real, as firegestures allows user to see the track of the mice movement.
trackpad gesture is when you can put fingers (currently 3) on trackpad and move them to operate browsers, its only available on newer mac lapstops, and firefox only supports it at version 3.1 beta.
Trackpad gestures can only do limited things, and so far, firefox 3.1 beta offers more gestures than safari on trackpad.
There is a system wide(?) plugin called multiclutch that can bring trackpad gestures to older version of firefox. But you still need newer macs that support such thing at hardware level.