Why are browsers saying that something is not trusted?

The Root Certificates and/or Intermediate Certificates may not be installed correctly. This can be checked by clicking on 'View Certificates' when you get the error message, and seeing if all three certificates are visible.

The certificate being used may not be for the Fully Qualified Domain Name. Check “View Certificates” again to see if the domain name on the certificate matches the domain name in the URL.

Check your Internet Option and make sure that “Use SSL 3.0” is ticked in the “Advanced” section, and check your .conf file to ensure that SSL Protocol version 3 is allowed.