Mac/Firefox: Delete key associated to browser "back" action

Only Firefox on Mac computers
The Delete key is associated to the "back" browser button. If you hit Delete on your keyboard, your browser will go "back" to the previous page.

Only Firefox on Pc computers

The Backspace key is associated to the "back" browser button. If you hit Backspace on your keyboard, your browser will go "back" to the previous page.

WORKAROUND FOR BOTH

You can fix this mis-assigned key by following those steps in Firefox :

1. In the Firefox address bar, type in about:config 
2. Click on "I accept the risk" button
3. Locate browser.backspace_action
4. Replace the value "0" with the value "2"

Your delete key will now be associated properly with the delete action.

Source : https://support.mozilla.org/en-US/questions/1202555