Firefox won't take me to the actual ticket purchasing page, claiming a certificate problem: tickets.events.ccc.de uses an invalid security certificate. The cer

Firefox won't take me to the actual ticket purchasing page, claiming a certificate problem: tickets.events.ccc.de uses an invalid security certificate. The certificate is not trusted because the issuer certificate is unknown. (Error code: sec_error_unknown_issuer) That's unfortunate. Doing s/https/http/ doesn't work either. Of course I guess all expected customers know how to add an exception to their browsers, but I couldn't be bothered when just browing out of curiosity. :)