For those that really need an earlier version of Firefox, find your system and the Firefox version you want in releases, download and start the install. * ftp://ftp.mozilla.org/pub/firefox/releases/ When reinstalling Firefox from a download, Firefox must be down once the installation starts. When the installation finishes, don't let the install start firefox for you. Instead end the install and start Firefox in your normal manner, thus preventing creating a new profile which does not have your bookmarks cookies, etc (but your old profile would still be around and would). ---- '''Keep your extensions up to date''', don't wait for a Firefox update and then try to do everything after the Firefox update. '''Research your''' extensions, some may have updates, some may be found in the developer comments or user comments on the add-on, or on the "'''View all versions'''" link which is part of the Release notes at the bottom of the add-on page. [https://addons.mozilla.org/firefox/addon/is-it-compatible/ '''Is It Compatible?''' :: Add-ons for Firefox], Are your add-ons compatible with the next version of Firefox? Find out straight from the Add-ons window! Only a few extension that worked in 4.0 won't work in Firefox 5. :You can force 5.0 "compatibility" with the "[https://addons.mozilla.org/en-US/firefox/addon/add-on-compatibility-reporter/ Compatibility Reporter]" extension, or with [http://kb.mozillazine.org/Extensions.checkCompatibility extensions.checkCompatibility] using about:addons.