Nagging Certificates In Safari

I am having a problem with the certificates in safari. For example I want to go to my gmail account and it always tells me that the certificate is not verified and it then asks me if I want to trust it. I obviously I do trust it and then I make sure that it always trusts it by clicking the little checkbox. And then I close safari and then open it again and it keeps nagging me. How can I fix this? I also tried to drag and drop the certificate and it still nags me. By the way this is not the only site that does this it is several of them.

Thanks for your help

The certificate was not 100% properly installed on the server. Safari and IE will always gripe. Firefox understands the minor problem and ignores it.