Mozilla is adding an extra layer of security in its Firefox browser by implementing HTTP Strict Transport Security (HSTS) The mechanism will force some sites into establishing a secure, HTTPS connection with the browser if its presented with the right certificate. Sites are culled from a list of hosts that have requested their sites be accessed by HSTS by default. The feature is currently in Firefox Beta, yet given its usual release schedule, should see the light of day in a few weeks in Firefox 17.
Source: https://threatpost.com/mozilla-adding-more-stringent-https-enforcement-firefox-110512/77183/