An ongoing project was started after Fx3.5 to improve startup time: <a href="https://wiki.mozilla.org/Firefox/Projects/Startup_Time_Improvements" rel="nofollow">https://wiki.mozilla.org/Firefox/Projects/Startup_Time_Impro...</a><p>You can also read the blog of the lead engineer working on startup time improvement: <a href="http://autonome.wordpress.com/" rel="nofollow">http://autonome.wordpress.com/</a>