In Firefox, go to the url: about:config (no space)
Find and set these values:
network.http.pipelining = true
network.http.pipelining.maxrequests = 100
network.http.proxy.pipelining = true
network.http.pipelining.firstrequest = true
network.http.request.max-start-delay = 0
besides that, I usually just leave the rest of the settings alone.. if you wanted to change some, they would be:
network.http.max-connections (default=24).. this should be good enough, may want to increase it if you open groups of bookmarks.
network.http.max-connections-per-server (default=8).. this should be good... too high hammers the server, too low takes too long to load the page.
network.http.max-persistant-connections-to-server (default=2).. this is the number of connections that stay connected.. like downloads... 2 at a time is good... might want to bump it to 3 or 4, too high will hammer the server.