You can see a special padlock at the left end of the location/address bar. *a padlock with a strike through means that mixed active content is blocked. *a padlock with an exclamation mark attached means that mixed passive content (e.g. images) is present, but not blocked. The shield icon, previously used for mixed active content, is now used for Tracking Protection. *https://support.mozilla.org/kb/mixed-content-blocking-firefox *https://support.mozilla.org/kb/control-center-site-privacy-and-security-firefox 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 affected. You can disable this feature in "Options/Preferences > Privacy" or via the about:privatebrowsing page that get when you open a New Private Window. *Options/Preferences > Privacy: "Use Tracking Protection in Private Windows" *https://support.mozilla.org/kb/tracking-protection-firefox *https://support.mozilla.org/kb/control-center-site-privacy-and-security-firefox ----- You can try these steps in case of issues with web pages: You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files. *Hold down the Shift key and left-click the Reload button *Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux) *Press "Command + Shift + R" (Mac) Clear the cache and remove the cookies from websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences). "Clear the cache": *Firefox/Tools > Options > Advanced > Network > Cached Web Content: "Clear Now" "Remove the cookies" from websites that cause problems. *Firefox/Tools > Options > Privacy > "Use custom settings for history" > Cookies: "Show Cookies" Start Firefox in <u>[[Safe Mode|Safe Mode]]</u> to check if one of the extensions ("3-bar" menu button or Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem. *Switch to the DEFAULT theme: "3-bar" menu button or Tools > Add-ons > Appearance *Do NOT click the "Refresh Firefox" button on the Safe Mode start window *https://support.mozilla.org/kb/Safe+Mode *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

cor-el, thanks for a quick and thorough response! I think Mozilla should make this Firefox behavior more noticeable to the users so that they'll know what to look for when this happens, rather than thinking that something's wrong with the webpage. A tiny gray shield icon near the address bar hardly indicates that it's the cause of the issue IMO.