The swishing tab animations in Firefox are pretty and all, but if you'd rather your computer concentrate on actual page loading rather than eye candy, there's a very simple
To disable tab animations, just type
about:config in your address bar, hit enter, and search for
browser.tabs.animate. Double click on it so that the value reads false, and close
about:config. From then on, tabs will open and close simply by appearing and disappearing, without any extra animations slowing it down.