Would you use a program that would reduce the memory usage of Firefox to 100-200 Kilobyte ?
Can you turn Firefox into a low burden on system resources?
Can you reduces the browser's craving for memory and CPU?
These is The Must Have Tool For ANY Firefox User! Make Firefox much faster. Try it and see for yourself!

Firefox Ultimate Optimizer
Firefox Ultimate Optimizer is a small tool that will dramatically reduce Firefox usage and therefore make your system faster and more stable. It doesn't require installation and stays unobtrusively in your system tray.

Firetune 1.2
Firetune is a program for optimising and tweaking Mozilla Firefox for your computer and internet connection.This process is as easy as selecting whether your computer and connection are fast or slow and Firetune does the rest.
Firetune recommens that you make a backup of your Firefox settings before making any other changes and it can do this for you. It can also restore a backup if you decide that the changes do not work for you. With the ability to roll back its changes and the fact that it is free, any self respecting Firefox user should give this a go.

Support for Firefox 1, 2, 3