Browser security errors, fixed

What each certificate and TLS error means for your visitors and how to fix it on your server.

• NET::ERR_CERT_DATE_INVALID

  The site's TLS certificate has expired or is not yet valid, judged against the visitor's device clock.

• NET::ERR_CERT_AUTHORITY_INVALID

  The browser does not trust the certificate authority that issued the certificate, or the chain to a trusted root is incomplete.

• NET::ERR_CERT_COMMON_NAME_INVALID

  The certificate does not cover the domain name the visitor typed, for example it covers example.com but not www.example.com.

• ERR_SSL_PROTOCOL_ERROR

  The browser and server could not complete a TLS handshake.

• ERR_SSL_VERSION_OR_CIPHER_MISMATCH

  The browser and server share no TLS version or cipher suite they are both willing to use.

• ERR_TOO_MANY_REDIRECTS

  The page keeps redirecting in a loop, so the browser gives up.

• NET::ERR_CERT_REVOKED

  The certificate authority has revoked the certificate, so browsers refuse it.

• SSL_ERROR_BAD_CERT_DOMAIN

  Firefox's version of a name mismatch: the certificate is not valid for the domain being visited.

• SEC_ERROR_UNKNOWN_ISSUER

  Firefox cannot build a chain from your certificate to a root it trusts.

• SEC_ERROR_EXPIRED_CERTIFICATE

  Firefox reports that the certificate has expired, or the visitor's clock is wrong.

• Mixed content

  An HTTPS page loads images, scripts or styles over plain HTTP.

• "Not secure" in the address bar

  The page is served over HTTP without TLS, or has insecure form fields.

• ERR_SSL_OBSOLETE_VERSION

  The server only offers TLS 1.0 or 1.1, which browsers no longer accept.