So the SSL certificate that I used to secure my website (and other things) is no longer trusted by Chrome (as of version 57), and so I have been forced to upgrade to a Lets Encrypt SSL certificate. It's almost as if I could have predicted this state of affairs in advance. At least I can now rest assured that my SSL certs will be easy to keep up to date (I have set up what I believe to be the required automated steps to do just that, time will tell).