How Do You Get Firefox to Utilize Secure HTTPS Connections by Default?
As an example, when I type superuser.com in Firefox’s address bar, it automatically goes to the HTTP version of the website when I really want the HTTPS version instead (by default).
An option you can try is the HTTPS Everywhere extension that is available for Mozilla Firefox, Google Chrome, and Opera. Since it is developed as a collaborative effort between the EFF and TOR project, I tend to trust and believe in this extension. It is also open source and available under the GPLv3 license.