Hi Lea, are you still able to use the site normally in Safari? If so, antivirus doesn't seem like a very likely culprit. Firefox has a Developer Tools panel with a Web Console that collects errors generated by scripts in web pages. You can open the console on the lower part of the tab for the site by pressing Command+Option+K. These messages aren't always useful, but if the site wants more information about what might be going wrong, you could share information from the Web Console with them. You also could test in Firefox's Troubleshoot Mode. In that 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 Troubleshoot Mode using either: * "3-bar" menu button > Help > Troubleshoot Mode... * (menu bar) Help menu > Troubleshoot Mode... and OK the restart. A small dialog should appear. Click the Open button. ''If Firefox is not running:'' Hold down the option/alt key while starting Firefox. A small dialog should appear. Click the Open 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? Ref. [[Diagnose Firefox issues using Troubleshoot Mode]]