http://www.askvg.com/ultimate-collection-of-best-aboutconfig-tweaks-for-mozilla-firefox-4-0/
user_pref("browser.allTabs.previews", true);
user_pref("browser.ctrlTab.previews", true);
user_pref("browser.download.manager.scanWhenDone", false);
user_pref("browser.fullscreen.autohide", false);
user_pref("browser.fullscreen.animateUp", 0);