Mouse Gestures

Firefox Mouse Gestures Plugin: Click and drag a mouse button to navigate web pages.

Go to the link above and click on the "Install Now" button in the middle of the page. It will install the plugin, and when it tells you to restart, go ahead, your session will be saved on restart.

If you use Windows or Linux, this is as far as you need to go.

On a Mac, do this to make it work: Tools Menu -> Add-ons -> (In the new window) Mouse Gestures -> Preferences