Are you looking for that? http://download.cdn.mozilla.net/pub/firefox/releases/

You can consider to install a portable (ESR) Firefox version to access websites if you need to use an older Firefox release version *http://portableapps.com/apps/internet/firefox_portable *http://portableapps.com/apps/internet/firefox-portable-esr *http://sourceforge.net/projects/portableapps/files/Mozilla%20Firefox%2C%20Portable%20Ed./ *http://www.freesmug.org/portableapps:firefox#toc1 *http://portableapps.com/support/firefox_portable#helper_apps *http://portableapps.com/support/firefox_portable#plugins