Is this about Tracking Protection? Firefox 42+ has a Tracking Protection feature that is enabled by default in Private Browsing mode. Firefox shows a shield icon at the left end of the location/address bar in case content is blocked by Tracking Protection, click the shield icon for more information. You can disable this feature in "Options/Preferences -> Privacy & Security" or via the <b>about:privatebrowsing</b> page that get when you open a New Private Window. *Options/Preferences -> Privacy & Security: "Use Tracking Protection in Private Windows" *https://support.mozilla.org/en-US/kb/tracking-protection-firefox *https://support.mozilla.org/en-US/kb/control-center-site-privacy-and-security-firefox ---- You can check for problems with preferences. *delete possible user.js and numbered prefs-##.js files and rename/remove the prefs.js file to reset all prefs to the default value including prefs set via user.js and prefs that are no longer supported in current Firefox releases *http://kb.mozillazine.org/preferences_not_saved *http://kb.mozillazine.org/resetting_preferences You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the <b>about:profiles</b> page. *Help -> Troubleshooting Information -> Profile Directory:<br>Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder *http://kb.mozillazine.org/Profile_folder_-_Firefox