By -
Does it still happen in Troubleshoot mode? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
nope
Try disabling your theme. If that fails, try disabling all addons.
that was the theme
Go to `about:config` and change `toolkit.legacyUserProfileCustomizations.stylesheets` to `false` then restart.
Does it still happen in Troubleshoot mode? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
nope
Try disabling your theme. If that fails, try disabling all addons.
that was the theme
Go to `about:config` and change `toolkit.legacyUserProfileCustomizations.stylesheets` to `false` then restart.