"Check the address for typing errors such as ww.example.com instead of www.example.com
   If you are unable to load any pages, check your computer’s network connection.
   If your computer or network is protected by a firewall or proxy, make sure that Firefox is permitted to access the Web."

During a session viewing https://www.washingtonpost.com/, I hit the "back" button and received the following error message: "Server not found "Firefox can’t find the server at www.washingtonpost.com. "Check the address for typing errors such as ww.example.com instead of www.example.com If you are unable to load any pages, check your computer’s network connection. If your computer or network is protected by a firewall or proxy, make sure that Firefox is permitted to access the Web." Chrome finds the page with no problem. I have attached screen shots of both. I think the problem may be due to my somehow telling Firefox that the connection to the Post is not secure. If you look at the address bar in both screen shots, you see that Firefox does not indicate a secure connection. Chrome does. The "back" button is immediately adjacent to field showing connection security. I suspect I accidentally changed the setting on Firefox for the Post, but am not sure. I cannot determine any means of correcting this. Firefox 49.0.2 Mac OS 10.12.1 NoScript 2.9.0.14 (settings for Washington Post unchanged)