Double click on a page to go back to the previous page. You can double click with your left mouse button by pressing the left mouse button twice in quick succession.
If there is no page to go back to, the current tab will close.
This addon does not work on these pages:
- about: pages
- privileged websites such as addons.mozilla.org (caused by security restrictions)
- Flash websites
Available for Firefox here: https://addons.mozilla.org/firefox/addon/double-click-on-page-goes-back/