Today I’ve read a marvelous way to make Firefox a whole lot faster, here is to do so:

Just follow these instructions — and don’t worry, if you mess it up, you won’t break anything.

• Type about:config into the address bar
• Type browser.cache into the Filter field
• Set browser.cache.disk.enable to false (double click it)
• Set browser.cache.memory.enable to true (double click it)
• Right click > New > Integer; type browser.cache.memory.capacity; press OK
• Type in 100000 (this is equivalent to 100 megabytes); press OK
• Close all Firefox tabs and windows, and then restart the browser

If you want more than 100 megabytes of cache — if you have lots of spare memory, or you’re prone to mammoth browsing sessions — type in 500000 instead for 500 megabytes of cache. To confirm everything is working, visit about:cache and you should see some ‘Memory cache device’ information.

This is tested with Firefox 3.7 & 4