Yes, you may be careful there, but you might play around with a few settings that are listed at the end of the text, which I copied from the Keychain Access help file.
But these certificates came there while making internet connections, so deleting one should initiate a new certificate next time you access that place. Tricky thing remains, which one is causing your problem.
quote:
Certificates have many uses. For example, a certificate might allow you to sign email, encrypt a document, connect to a secure network, or identify yourself on iChat. Each type of usage is governed by a trust policy, which determines whether a certificate is valid for that use. A certificate may be valid for some uses but not for others.
Mac OS X uses a number of built-in policies to determine whether a certificate is trusted:
X.509 Basic Policy: The certificate must be part of a valid chain whose root is in the trusted X509Anchors file.
Secure Sockets Layer (SSL): The name in a server's certificate must match its DNS host name to successfully establish a connection. The host name check is not performed for SSL client certificates. If there is an extended key usage field, it must contain an appropriate value.
Secure Mail (S/MIME): When signing or encrypting, the user's email address must be listed in the certificate, and certain key usage fields must be present.
Extensible Authentication (EAP): When connecting to a network that requires 802.1X authentication, the name in the server's certificate must match its DNS host name. The host name check is not performed for client certificates. If an extended key usage field is present, it must contain an appropriate value.
Code Signing: The certificate must contain key usage settings that explicitly permit it to sign code.
IP Security (IPsec): When certificates are used to secure IP traffic (for example, in establishing a VPN connection), the name in the server's certificate must match its DNS host name. The host name check is not performed for client certificates. If an extended key usage field is present, it must contain an appropriate value.
iChat Security: The certificate must contain key usage settings that allow it to be used for iChat.
You can change these policies on each certificate, providing a greater amount of control over how certificates are evaluated.
To view or change a certificate's trust settings:
Open Keychain Access.
Select a certificate, then click Info ℹ or double-click the certificate in the list.
Click the Trust Settings disclosure triangle to display the available trust policies for that certificate.
To override the policy, select a new trust setting from the pop-up menu.
