I did a other topic on way to speed up firefox but is better.
I'm using firefox 3.5. beta4 for Linux. but this work with Mac, windows or Linux. an is for all versions of firefox.
step 1 type in "about:config" into your address bar.
you'll get this screen, click "I'll be careful, I promise!"

now you'll get this screen

type into the filter bar "network.http.pipelining" click on it an make it true.

go down to "network.http.pipelining.maxrequests" and make it 8.

type in to the filter bar "network.http.proxy.pipelining" click on it and make it true.

Now type in to the filter bar "network.dns.disableIPv6" click on it and make it true.

type in to the filter bar "plugin.expose_full_path" an make it true.

Now we are going to add somethings. Now right click on anything -> New -> Integer

And then type in "nglayout.initialpaint.delay"

For the value type in "0"

again right click on anything > New > Integer and type in "content.notify.backoffcount"

For the value type in "5"

again right click on anything > New > Integer and type in "ui.submenuDelay"

For the value type in "0"

Now we are going to mod the mount of RAM FireFox uses.
Right click on anything > New > Integer and type in "browser.cache.memory.capacity"

For the value type in "16384" this means 16MB

OK i did some Benchmarking i forgot to take a screen shot. but I got 384 that was stock.
with the mods i got 453
If got any questions about windows 7,vista,XP or Ubuntu\Linux feel free to Email me at bigcj9087@live.com or PM me on the forum.