This is a great tweak.

1. With Firefox up and running, type about:config and hit enter.
2a. Find the entry called “network.http.pipelining” and set it to “true”.
2b. Find the entry called “network.http.proxy.pipelining” and set it to “true”.
2c. Find the entry called “network.http.pipelining.maxrequests” and set it to 16-32, but beware, if set too high you may risk banning yourself from various servers by being mistaken for a DoS attack.
3. Restart your browser.

Source:Gomeler.com - Visit the site for other great Firefox tweaks.