i was looking around for usefull settings and came across these.
these might improve browser performance. i changed pipelining and max connections and initialpaint - made a huge difference for me.
user_pref("content.notify.backoffcount", 200);
user_pref("content.notify.interval", 100);
user_pref("network.cookie.lifetime.days", 5);
user_pref("network.http.max-connections", 60);
user_pref("network.http.max-connections-per-server", 32);
user_pref("network.http.max-persistent-connections-per-proxy", 16);
user_pref("network.http.max-persistent-connections-per-server", 15);
user_pref("network.http.pipelining", true);
user_pref("network.http.pipelining.firstrequest", true);
user_pref("network.http.pipelining.maxrequests", 100);
user_pref("network.http.proxy.pipelining", true);
user_pref("nglayout.initialpaint.delay", 0);
discussions about speed settings w/ explanations and more options...