hold down the Shift key and left-click the Reload button   

   Settings -> Privacy & Security
   Cookies and Site Data: "Manage Data" 

   Settings -> Privacy & Security
   Cookies and Site Data -> Clear Data -> [X] Cached Web Content -> Clear 

   https://support.mozilla.org/en-US/kb/clear-cookies-and-site-data-firefox
   https://support.mozilla.org/en-US/kb/how-clear-firefox-cache 

   switch to the Default System theme: "3-bar" menu button or Tools -> Add-ons -> Themes
   do NOT click the "Refresh Firefox" button on the Troubleshoot Mode start window 

   https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
   https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems 

   click the shield icon for more detail and possibly disable the protection 

I've added https://x.com as an exception site but it is still blocked. https://x.com/mozilla doesn't work either Error message on the page: "Something went wrong, but don’t fret — let’s give it another shot. ⚠️ Firefox’s Enhanced Tracking Protection (Strict Mode) is known to cause issues on x.com" After 2 days it used to finally load without my doing anything, but not now. I never loads using Firefox. https://x.com is added as an exception, but obviously ignored. Tried You can reload webpage(s) and bypass the cache to refresh possibly outdated or corrupted files. hold down the Shift key and left-click the Reload button NOPE Tried: Clear the Cache and remove the Cookies for websites that cause problems via the "3-bar" Firefox menu button (Settings), click the padlock icon (Clear cookies and site data) for the domain in the selected tab. "Remove the Cookies" for websites that cause problems: Settings -> Privacy & Security Cookies and Site Data: "Manage Data" "Clear the Cache": Settings -> Privacy & Security Cookies and Site Data -> Clear Data -> [X] Cached Web Content -> Clear https://support.mozilla.org/en-US/kb/clear-cookies-and-site-data-firefox https://support.mozilla.org/en-US/kb/how-clear-firefox-cache Start Firefox in Troubleshoot Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration or if userChrome.css/userContent.css is causing the problem. switch to the Default System theme: "3-bar" menu button or Tools -> Add-ons -> Themes do NOT click the "Refresh Firefox" button on the Troubleshoot Mode start window https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems NOPE - lost all my bookmarks, extensions, settings - not going there again thank you as for: You can check for issues with Enhanced Tracking Protection. Firefox shows a purple shield instead of a gray shield at the left end of the location/address bar in case Enhanced Tracking Protection is blocking content. click the shield icon for more detail and possibly disable the protection the sheild has a slash thru it saying "enhanced tracking is off for this site" when i put my mouse over it.