That checkbox actually is inside the Options dialog itself. "3-bar" menu button (or Tools menu) > Options Click Privacy at the top to open the Privacy panel Then if your setting is something other than "Firefox will: Use custom settings for history" go ahead and select custom so you can access the individual features. But... that might not be related to your problem. There are two possible issues that come to mind: (1) Address bar autofill If you start typing a site, Firefox will suggest a URL in the address bar and may substitute HTTPS for HTTP. If you edit carefully, you can avoid this. You also can turn off the feature of filling in a suggestion in the address bar itself if this is a regular annoyance. (More on that if you're interested.) (2) Website sent a strict transport security (STS) header Websites can specify that only HTTPS should be used and Firefox will honor this. Sometimes users have discovered that only one application on a server cares about this, but Firefox stores it as a global setting for the site. This can be cleared by using the somewhat drastic "Forget about this site" feature. However, it might come right back. You can access "Forget about this site" in any of the following places: * Library dialog (Ctrl+Shift+h), right-click menu for a history entry * History sidebar (Ctrl+h), right-click menu for a history entry * about:permissions page Because this feature scans your entire history, bookmarks, cookies, site-specific permissions, etc., do not be alarmed if Firefox locks up for a minute while clearing all traces of the site.