Do this in about config, it will get you much faster speeds. Imo its a requirement.
Go to about:config. Enter http in the filter and hit enter. Look for network.http.pipelining. Double click it so it becomes true. Now look for network.http.pipelining.maxrequests. Double click it and a dialog box will pop up with the number 4 in it. Change this number to 100. Restart firefox. You will notice a high speed increase.