I recently installed Ubuntu 10.04, and found that pressing backspace no longer takes me to the previous page in Firefox. Thankfully, there is a way to fix this.
Type about:config in the address bar and press the Enter key. A warning page will open. Click the "I'll be careful, I promise!" button.
In the filter type browser.backspace_action and then right-click on the entry and click "Modify". Enter 0 (zero) in the box and click OK.
