forevergeek.com has a useful guide on speeding up firefox for broadband users. basically after getting to the hidden config settings you set the browser to request more data that it usually does.
1.Type “about:config” into the address bar and hit return. Scroll down and look for the following entries:
network.http.pipelining network.http.proxy.pipelining network.http.pipelining.maxrequests
Normally the browser will make one request to a web page at a time. When you enable pipelining it will make several at once, which really speeds up page loading.
2. Alter the entries as follows:
3. Lastly right-click anywhere and select New→ Integer. Name it
You shouldn't have to type out the whole thing, as the listings change dynamically as you're typing. Simply double-click on the entry to change the default value of “False” to “True”. Render pages faster
5. If you reduce the amount of web history that Firefox stores, it will load faster and also save you some disk space. Type the following in the search bar: browser.history and change browser.history_expires_days and browser.history_expires_min to 1. You can also use low numbers if you want to keep some browser history.