Howto: do 'page back' instead of 'page up' when backspace is pressed in Mozilla Firefox

In Firefox, when you press 'Backspace' the default action performed is 'Page up'.
You can change this to 'Previous page', just follow this for that:

• In the adress bar in Firefox type:

  about:config

• Search for 'browser.backspace_action' in the list
• Change the value from 1 to 0 by doubleclicking on the number
• Restart Firefox