In the browser’s address bar, input this reserved address for advanced configuration: about:config. You will see a warning like “Changing advanced configuration preferences can impact Firefox performance or security.” Click on the continue button.
Now you can see a search bar where you can input a configuration key and set a different value than the default one. Most of the default values makes sense, but here are the ones I choose to change:
Shortcut: backspace key goes to last page
browser.backspace_action defines the behaviour when you press the Backspace key. It won’t affect the behaviour to delete the last character when you are typing in a form, though. I like to change it to “Go back to last page”. Here are the values you can specify:
0Go back to last page in history, like clicking on the left arrow on the tool bar.1Behaves the same asPageUpkey.2Disable it. (Default)
It’s also worth mentioning that Shift + Backspace behaves the opposite accordingly: Go forward in history (0), or PageDown (1).
Mouse: double click to close tab
browser.tabs.closeTabByDblclick controls whether double clicking on a tab closes it. It’s a pretty handy feature sometimes. Simply set it to true and it’ll work on new tabs.