Forget the preferences hacks, the FasterFox extension for Firefox does all those nice little speed tweaks so that webpages load really fast. What's more just to prove that things are running faster there it has a little page load timer on the bottom of the Firefox window. Tweaking Firefox is simple with this extension, just go into your Preferences and in the FasterFox tab select the tuning setting you would like and the changes are made for you.