(it might be good but not for sure) The certificate is for another domain Check the actual domain for which the certificate is issued. The certificate is not verified by a trusted CA The certificate is issued/signed by an authority that your browser does not trust. (for example, my institute uses HTTPS for its mail site webmail.iitk.ac.in but is not signed by one of the authorities that popular browsers trust) The remedy is to visit the website of the certificate signer (that must be HTTPS) and confirm that the certificate is issued by it and if you trust the signee enough go ahead and add the certificate to the browser repository.