When I updated Safari from version 5 to version 6 I discovered the backspace key to go back to the previous page doesn’t work any longer. I’ve always used backspace for that purpose (when not entering text into a form), so here is how it is fixed:
http://hints.macworld.com/article.php?story=20120727025535867
In short:
defaults write com.apple.Safari NSUserKeyEquivalents -dict-add Back "\U232b"