This happens when the common name to which an SSL Certificate is issued (e.g., www.example.com) doesn't exactly match the name displayed in the URL bar. Any difference will cause the web browser to halt and display a name mismatch error. This error can happen even if the correct certificate is installed properly. For example, you connect to the website via the IP address or an internal name but the certificate was issued to the fully-qualified domain name (or vice versa).
If your website is secured by a certificate with the name www.example.com you will receive this error if you connect using any of the following names:
example.com
example.local
208.77.188.166
10.1.1.7
Even though all of the above addresses would get you to a site with a valid certificate, you could still get a name error if you are connecting to a name other than the one (CN) that the certificate was issued to.