This forum detected your operating system as Windows Vista. Check that you do not run Firefox in compatibility mode. You can open the Properties of the Firefox desktop shortcut via the right-click context menu and check the "Compatibility" tab. Make sure that all items are deselected in the "Compatibility" tab of the Properties window. See also: *https://support.mozilla.org/en-US/kb/how-reset-default-user-agent-firefox *https://support.mozilla.org/en-US/kb/Finding+your+Firefox+version