Let me start this off by saying this is not an ideal trick and one I hope no one else needs to use because it's a bad idea to work around a browser feature that's aimed to protect your security.
That said, I am in the process of testing a product and ran into a weird situation where our team had to revoke the SSL certificate we had assigned to our server. We're going to replace it but I have testing to do in the meantime and need access to our staging server, so waiting is kind of a blocker because, well, this message gets me nowhere.
I run most of my production sites with forced SSL, including CSS-Tricks. But locally, I've avoided getting SSL working properly. I've always avoided it, perhaps because it's not immediately obvious how to do it. It's also not that big of a deal since it's just local traffic. But hey, might as well make local work as close to production is possible eh?