I got this from telenet a while ago:
open notepad and copy the following into it:.
user_pref("content.interrupt.parsing", true);
user_pref("content.max.tokenizing.time", 2250000);
user_pref("content.maxtextrun", 8191);
user_pref("content.notify.backoffcount", 5);
user_pref("content.notify.interval", 750000);
user_pref("content.notify.ontimer", true);
user_pref("content.switch.threshold", 750000);
user_pref("nglayout.initialpaint.delay", 0);
user_pref("network.http.max-connections", 48);
user_pref("network.http.max-connections-per-server", 16);
user_pref("network.http.max-persistent-connections-per-proxy", 16);
user_pref("network.http.max-persistent-connections-per-server", 8);
user_pref("network.http.pipelining", true);
user_pref("network.http.pipelining.maxrequests", 100);
user_pref("network.http.proxy.pipelining", true);
save as user.txt on the following location:
C:\documents and settings\username\application data\mozilla\firefox\profiles\default
username is the name of the target account, not the word username
rename user.txt to user.js
settings will take effect the next time you start firefox.