2. Render quickly
Large, complex web pages can take a while to download. Firefox doesn't want to keep you waiting, so by default will display what it's received so far every 0.12 seconds (the "content notify interval"

. While this helps the browser feel snappy, frequent redraws increase the total page load time, so a longer content notify interval will improve performance.
Type about:config and press [Enter], then right-click (Apple users ctrl-click) somewhere in the window and select New > Integer. Type content.notify.interval as your preference name, click OK, enter 500000 (that's five hundred thousand, not fifty thousand) and click OK again.
Right-click again in the window and select New > Boolean. This time create a value called content.notify.ontimer and set it to True to finish the job.