Some web sites require you have a special "certificate" to access the site. This typically occurs with higher security sites, such as a corporate web site for employee access only. It appears you have the certificate, but it not usable.
Example
Server Error
403.16 - Forbidden: Client certificate is ill-formed or is not trusted by the Web server.
Your client certificate is untrusted or invalid. A Secure Sockets Layer (SSL) client certificate is used for identifying you as a valid user of the resource.
Error messages will differ depending on the web server and if replaced by the web site designers.
Occurrences
Frequency is relative to other Internet warnings and errors.
Solutions and Fixes
Get New Certificate
9
You will need to contact the web owners to get a new certificate (what is called a client SSL certificate).
FaultWire Staff Posted: 26-Oct-2008
Official Explanation
The client browser tries to use a client certificate that is not trusted by the server that is running IIS 7.0 or that is not valid.
"403.16 - Client certificate is untrusted or invalid" is only supported by Microsoft IIS (Internet Information Services) web servers.
The four hundred series of errors indicate something was sent to the remote web server incorrectly.
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The client browser tries to use a client certificate that is not trusted by the server that is running IIS 7.0 or that is not valid.
