For those that really need an earlier version of Firefox to '''test with''', find your system and the Firefox version you want in releases, download and start the install. * ftp://ftp.mozilla.org/pub/firefox/releases/ :or with the latest of version 3 * http://www.mozilla.com/firefox/all-older.html : Note Mac OS X 10.4 user, and Mac OS X 10.5 users without Intel cannot upgrade to Firefox 4 or 5. 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 your '''test install''' of 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). <br><small>Please mark "Solved" one answer that will best help others with a similar problem -- hope this was it.</small>