Start Faster is an awesome add-on that it’s developed by an official Firefox developer.
In the beginning this add-on had to be integrated in the next Firefox 4 beta release, but it wasn’t so this guy released his idea as a Firefox Add-on so people can benefit from it while they figure out how to properly integrate it into Firefox.
Think of this as a work-in-progress technology preview.
Start Faster bypasses the Windows prefetch feature to start Firefox faster.
It adds a ‘faster firefox’ shortcut to the Desktop which should launch Firefox up to 2x faster than without this addon.
This add-on requires Windows 7/Vista and Firefox 4.0b10pre or later.
I found some other ways to speed up firefox http://howtohacklife101.blogspot.com/2011/05/how-to-make-firefox-faster.html