Gah-Your-tab-just-crashed https://support.mozilla.org/en-US/kb/troubleshoot-firefox-crashes-closing-or-quitting

They load in safe mode, but they do not load in normal mode with all extensions disabled, the default theme selected, and hardware acceleration turned off.

https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode

Safe Mode is a troubleshooting mode that temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes), any userChrome.css/userContent.css files, and some other advanced features to help you assess whether these are causing the problem. If the problem goes away, that tells us one thing. If it does not, that tells us something else. +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Use these links to create a new profile. Use this new profile as is. Is the problem still there?

https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

http://kb.mozillazine.org/Profile_folder_-_Firefox#Navigating_to_the_profile_folder

https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

Type about:profiles<enter> in the address bar.

I tried creating a new profile and launching using that profile, with no changes to it. Firefox crashed on launch. Same thing if I tried "launch profile in new browser."

I was able to get back into Firefox by launching in safe mode, disabling hardware acceleration in the test profile, and relaunching in normal mode. However, going to any of the "forbidden" sites still causes the tab to crash.

Does Private Browsing mode make a difference?

You can check the connection settings.

• Settings -> General -> Network: Connection -> Settings

If you do not need to use a proxy to connect to internet then try to select "No Proxy" if "Use the system proxy settings" or one of the others do not work properly.

See "Firefox connection settings":

• https://support.mozilla.org/en-US/kb/websites-dont-load-troubleshoot-and-fix-errors
• https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can
• https://support.mozilla.org/en-US/kb/firefox-and-other-browsers-cant-load-websites

You can try to disable WebRender via these prefs on the the about:config page to see if that has effect.

• gfx.webrender.enabled = false
• gfx.webrender.compositor = false

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

Private Browsing does not help. I'm not using a proxy, but I tried forcing it off to be sure; naturally, that did not help. gfx.webrender.enabled and gfx.webrender.compositor were already both false.