You ruled out add-ons as an issue by testing in Firefox's Troubleshoot Mode? Or some other method? If you haven't already: (1) Clear Firefox's Cache See: [[How to clear the Firefox cache]] -- just clear Cached Web Content If you have a large hard drive, this might take a few minutes. (2) Remove the problem site's cookies (save any pending work first). While viewing a page on the site, click the lock icon at the left end of the address bar. After a moment, a "Clear Cookies and Site Data" button should appear at the bottom. Go ahead and click that. In the dialog that opens, you will see one or more matches to the current address so you can remove the site's cookies individually without affecting other sites. Then try reloading the page. Does that help? '''Testing in Firefox's Safe/Troubleshoot Mode:''' In this mode, Firefox temporarily deactivates extensions, hardware acceleration, any userChrome.css/userContent.css files, and some other advanced features to help you assess whether these are causing the problem. ''If Firefox is running:'' You can restart Firefox in Safe/Troubleshoot Mode using either: * "3-bar" menu button > Help > Troubleshoot Mode... (before Fx88: Restart with Add-ons Disabled) * (menu bar) Help menu > Troubleshoot Mode... (before Fx88: Restart with Add-ons Disabled) and OK the restart. A small dialog should appear. Click the Open button (before Fx88: "Start in Safe Mode" button). ''If Firefox is not running:'' Hold down the Shift key when starting Firefox. (On Mac, hold down the option/alt key instead of the Shift key.) A small dialog should appear. Click the Open button (before Fx88: "Start in Safe Mode" button). ''Note: Don't use the Refresh without first reviewing this article to understand what will be deleted:'' [[Refresh Firefox - reset add-ons and settings]]. Any improvement?