Name Mismatch Error indicates that the Common Name (domain name), which is provided in the certificate does not match the address that appears in your browser. Following is a basic example which will be helpful to understand this error: Should the certificate is issued to www.paypal.com address and you try to access site without the www, you will get a SSL-certificate error.
Vast majority of domain owners are willing to drive traffic from an address without the “www” to address with “www”. This is helpful in order to avoid mistakes associated with Name Mismatch Error. This error could be bypassed by obtaining a certificate with SAN. You can get a certificate for paypal.com address and include the address SAN www.paypal.com, to avoid error.
Another common example of Name Mismatch Error would be having an access to the server by its internal name and the SSL certificate installed just for the public name. In these circumstances, you can get a certificate UC, which will include the internal name and a public server.
Most browsers will display an error message for the purpose of warning the user, because in the case of phishing, users can get the fake site. This error would be shown in various ways depending on the browser. For example, the error may have the following form: the site uses the wrong security certificate.
It would be better to refer to the site administrator in order to resolve these issues in the future.