If I record correctly, Mozilla has said that like 97% of all problems people has is with problems is due to extensions, not Firefox. '
When you have a site not working as expected, start Firefox in "Troubleshoot Mode" (alt-key then in the menu at the top Help > Troubleshot mode) that starts Firefox with addons turn off. If the site works, restart and turn of addons one by one to you see which one creates the problem.
When you have a site not working as expected, start Firefox in "Troubleshoot Mode" (alt-key then in the menu at the top Help > Troubleshot mode) that starts Firefox with addons turn off. If the site works, restart and turn of addons one by one to you see which one creates the problem.