Hello, I am using Firefox 78.15.15.0 esr (64 bit) on an iMac Desktop with OS X ElCapitan 10.11.6 When I try to open any bookmark or anything with an URL I get only a blank Tab. In Preferences I can see all my Bookmarks, History, Home page URL, Firefox Home, Cookies and Site data. The Applications box contains only; irc always ask, ircs always ask, mailto use mail and PDF open in firefox. I Refreshed Firefox and got the Old Firefox Data folder. The files for Bookmarks, Downloads, Browsing History, Passwords, and Cookies all have the same values in the Old and Current Profiles. File types "handlers.jason" value is 2KB in the Old and 540 bytes in the Current. I also tried restarting in Safe Mode with no improvement. I have read through most of the articles and links but not being an expert can't see a clear step by step path to resolution. I would appreciate any help you can give to resolve this matter. Thank you. Pete Problem has been resolved. No help from the Mozilla Community.