When connecting to a URL via HTTPS and the SSL certificate doesn't match (such as at a paid Wi-Fi hotspot), iOS shows a dialog asking whether the certificate should be accepted. If you accept the certificate, iOS adds an SSL exception and will never ask about that certificate again.
There are possibly two aspects to this: certificates accepted in Safari, and certificates accepted for network services in other apps.
The question is, how does one remove these exceptions, short of a full device reset? There seems to be no way to view or remove exceptions in the device settings.
Best Answer
You can delete the SSL certificate.
Go to Settings → General → Reset → Network Settings.
This resolves the problem.
[EDIT]
As of iOS 10.3.2 this does NOT work. Instead it wipes out your network settings, but does NOT remove certificate exceptions.