Screaming Penguin - Source Does Matter

Mouse gestures are very interesting. Basically a mouse gesture is a recognized sequence of movements from the mouse that then causes an action (up, up, down, etc.)

The official explanation is thus: "Mouse movements in combination with a click-hold and optionally a modifier that execute some browser functions. You press mouse button (plus modifier, if you have configured it like this), draw a gesture and release mouse button. This gesture is recognized and appropriate action is triggered."

There is a package for Mozilla, called MozGest, that allows the usage of mouse gestures. Check out more via the linked MozDev project page for the project sponsor, OptiMoz.   Mouse Gestures