If you are coming from windows and moving onto linux you might be used to press backspace to go back one page in Firefox. Well you’re in for a small surprise – id doesn’t work.
You need to go to about:config
browser.backspace_action as either 0 or 1.
0 means that the backspace button will go back a page in the session history
1 means that pressing the backspace key will scroll up one page in the current document