I have received several notices telling me that I was running an older version of Firefox and that I should update. I was running Firefox 78 on a 2007 iMac version 10.11.6 I downloaded the newest version of Firefox, 91 and without checking I replaced my 78 version. I found out later that Firefox 91 will not run on my iMac as it is not running version 10.12 or higher. My machine is too old to upgrade beyond 10.11.6 I would like to download Firefox 78. Actually I would prefer to reinstall 78 so I could retain my bookmarks. Is this possible? I have tried to find a version 78 to download but keep getting version 91.