Yesterday we wrote about moving the cache of Firefox or Chrome onto a RAM disk. Instead of loading cached images and data from the hard drive, it loads from memory, which is a lot faster. It turns out, though, that Firefox can do this without using a RAM disk -- you can simply do it with about:config.
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.
I'm currently unable to benchmark this change (Firebug doesn't work with FF4 Beta 7!) but in theory it should be just as fast or faster than the RAM disk approach.. Lee has been using it for a few hours and he says page loads are much faster. If you use Firefox, try it out and let us know whether it feels faster or not!