I don't know if this is applicable, but there's a lot of talk about SSL certificates, so I thought I'd add this tidbit ... if you're constantly being hounded by Safari or Mail.app that it does not recognize a certificate, you can use the previously posted hints to install that certificate or it's signing certificate into Mac OS X to eliminate the warning. However, to do that, you need to have the certificate. Here's an easy way to get the certificate itself: open a Terminal window and type the following:
openssl s_client -showcerts -connect hostname.com:port
For example, if you wanted to get the certificate for www.verisign.com, you'd do this:
openssl s_client -showcerts -connect www.verisign.com:443
You will see quite a bit of output from this, but the first block beginning with
-----BEGIN CERTIFICATE----- is the certificate for the server. Copy everything from (including) the
BEGIN CERTIFICATE line to the corresponding
END CERTIFICATE line, and save it into a file that ends with
.cer. Now you've got a certificate file for that server! Follow the previous hints to install it in the appropriate Keychain.