If you use a very small laptop, you’re likely to be missing some keys that are normally available on a full keyboard. On my Eee PC, Asus didn’t have room for PageUp and PageDown keys, and replaced them with a function key equivalent of Fn-Up and Fn-Down.

I normally use PageUp and PageDown a lot in Firefox. PageDown can be easily replaced with the space bar, but what about PageUp? Here’s the fix:

In Firefox, navigate to about:config Type backspace into the Filter box. Double-click on the browser.backspace_action entry, and change the value from 2 to 1 Now you can use spacebar as PageDown, and Backspace as PageUp.