How to remove SSL exception Safari
I had this issue come up recently when traveling out of town, and having issues connecting to hotel WiFi, and in doing so did some IP sniffing, and trying to get onto a site via IP, which had a certificate mismatch, which I first added an exception to.

To get to the bottom of it, I first got info from the certificate in the browser, but nothing turned up in Keychain access looking for that. What I did to fix this was click on the lock icon in the URL bar, then clicked on Show Certificate. In that window, go to Trust > When using this certificate, and click on the ? icon to the right of the settings, which brings up a Mac Help window, which if you click on the link Open Keychain Access for me, where you can see the certificate highlighted in the Keychain Access listing. Tap the info button on the bottom of the screen, and from that window click to expand Trust, then change When using this certificate to Use System Defaults. Once this is done, flush your caches, close and restart the browser, and test to confirm.

Here's a screen capture with that first info button highlighted: