Speed Up Firefox

Firefox is a powerful browser with extensions to do almost anything, but it's never been accused of being light on resources—and limiting your history size can help.

Every time your browser requests a page or image from anywhere, that data is stored in your browser history for a default of 90 days—for most of us that translates to an enormous amount of data stored in the internal history database. The Mac Tips and Tricks weblog has a quick and very useful tip to make Firefox load more quickly—just visit Preferences -> Privacy -> History and turn the dial down to a more reasonable 5-10 days. You'll need to clear your history or restart Firefox after you make this change, but in my testing the startup speed improved significantly.

If you want to keep your entire computer clean instead, you can set reader favorite CCleaner to run silently with a keyboard shortcut, or set it up to run on a schedule for hassle-free system cleaning—just make sure to include Firefox in your CCleaner profile.
Source: Lifehacker.com