"Untrusted connection" means the connection has been secured, but the information on the protection's certificate does not match the site or is otherwise incorrect (expired, for example). I get a green lock icon (connection trusted, secure) on Firefox 41.0 on Facebook, so this sounds unusual. You've checked Firefox 30.0 as your version, could you update your Firefox and see if that clears things up?

http://www.ehow.com/how_11385212_troubleshoot-reset-connection-firefox.html https://support.mozilla.org/en-US/kb/server-not-found-connection-problem https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message https://support.mozilla.org/en-US/kb/connection-untrusted-error-message '''http://kb.mozillazine.org/Error_loading_websites''' '''This Connection is Untrusted''' is sometimes caused because the computer system clock is wrong. Check the time / date / time zone settings.