This was a great add-on when first created, but lack of innovation has made it fall behind over the years. I quit using it a while ago in favor of Smart HTTPS, which does the same thing but provides two very important extra features: it automatically retries without HTTPS if the page fails to load, and it whitelists the site so it won't try again next time. This allows you to have the safety of using HTTPS when possible, but also prevents breakage, which can range from annoying to problematic (in the case of a basic user). It's a shame this add-on never provided similar functionality, as I'd prefer to use it over the other due to being provided by the EFF vs some random developer.