Hi, this message could refer to any extension that blocks content in pages, or to Firefox's built-in Tracking Protection feature. (1) Checking Extensions Extensions such as Adblock Plus, Blur, Disconnect, DuckDuckGo Privacy Essentials, Ghostery, NoScript, Privacy Badger, uBlock Origin or uMatrix may block required elements on a site. Usually you can find a toolbar button for each add-on to manage blocked content in a page. There may or may not be a number on the icon indicating the number of blocked items; you sometimes need to click the button to see what's going on and test whether you need to make an exception for this site. (2) Tracking Protection The shield icon toward the left end of the address bar usually turns a bit purplish when content is blocked. Click the icon to learn more or make an exception (you can click the blue slider switch to disable protection). See: [[Enhanced Tracking Protection in Firefox for desktop]].