I cannot access GMail because I get the 'This Connection is Untrusted' page. The Technical Details are: mail.google.com uses an invalid security certificate. The certificate is not trusted because the issuer certificate is not trusted. (Error code: sec_error_untrusted_issuer) If I click 'Add Exception', in Certificate Status, it says, 'This site provides valid, verified identification. There is no need to add an exception.' My machine is on a corporate site, behind a firewall and proxy server. The proxy server substitutes the certificate so although it's called mail.google.com, it's issued by our internal CA. I've added the internal CA certificate to the Authorities list (by importing it to Servers and then selecting 'Trust the authenticity of this certificate').