It drives me nuts that I cannot hit command-left-arrow, and command-right-arrow for going back and forward in Firefox when the cursor is in a text field which is always the case when navigating Google search results thanks to some javascript that sets the focus on the search field. Finally I found an alternative:

Back: command-[
Forward: command-]

If I remember correctly I started to have this problem with alt-left-arrow, alt-right-arrow on Firefox for Windows so maybe alt-[, alt-] will also be a fix for those of you suffering in Windows.

Also, I’ve always missed a page up, page down buttons on my Macbook Pro and just found these handy tools:

Page Up: spacebar
Page Down: shift-spacebar