After installing Firefox 2, I noticed that the backspace key no longer worked as my beloved "Back" function, but now worked as Page Up.
Not satisfied with this turn of events, I went on the prowl on the internet, and found out how to change it back.
Thanks go to carthik of http://ubuntu.wordpress.com!
Clearly this is all a matter of preference, but I hope this helps anyone who preferred it the other way, and searched here first.
1) Type "about:config" in the address bar, and press enter.
2) Type "browser.backspace_action" in the filter bar. One result should come up.
3) Double click it and change the value to zero.
4) Close the configuration window, and enjoy!
I've only tried this on Ubuntu 6.06 LTS with Firefox 188.8.131.52
Edit: Last picture fixed, and made it a tad more presentable. >_>