My browser should do what I want it to do, not what it thinks is best for me. Unfortunately most browsers are going the way of trying to do things for the user so I expect this will get worse. Very annoying.
I ran into an issue where I had played around with signing certificates for localhost stuff and so firefox and noticed something went over https. When I removed the certificate for other reasons, firefox wouldn't let me connect to my things. It would redirect to the https even though the server had changed. I cleared the history, site preferences, used private browser and nothing worked. I verified that curl would work and Chrome worked which proved this was a firefox specific issue.
I searched around and finally found the setting that was responsible.
Go to the firefox configuration page:
about:config
Set network.stricttransport.security.preloadlist to false.
It's frustrating when my browser does stuff thinking it knows better. I'm sure there are other things firefox does that helps me quite a bit so I'm not sure what the balance should be. Though I think if the server changes its certificate process then that should take precedence.