After installing the Firefox 12, I have decided to put my all time favorite add-on to this browser and that is force tls. This add-on serves all websites via HTTPS in the future. This will help you in terms of insecure session with certain sites. This add-on is also compatible with Strict Transport Security. Then I have added the YahooMail URL to in order to force the window to open it with https but I could not able to get it open. For that reason I have removed the force tls add-on from Firefox. Even after this also, I am not able to open the YahooMail since it always defaults to https. I can open the YahooMail in other browser and there won’t be a problem.