Firefox 42+ has a Tracking Protection feature that is enabled by default in Private Browsing mode. When you are in private browsing mode then Firefox can show a shield icon at the left end of the location/address bar that some content is blocked. You can disable this feature in "Options/Preferences -> Privacy" or via the <b>about:privatebrowsing</b> page that get when you open a New Private Window. *Options/Preferences -> Privacy: "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 set this pref to true on the <b>about:config</b> page to see more Tracking Protection choices in "Options/Preferences -> Privacy". *privacy.trackingprotection.ui.enabled