CA of StartSSL is unknown

Hi,

The css-checker does not know the CA-certificate of StartSSL ( 
https://www.startssl.com/ )

The given error is:
http://jigsaw.w3.org/css-validator/validator?uri=https://www.startssl.com/

I/O Error: sun.security.validator.ValidatorException: PKIX path building 
failed: sun.security.provider.certpath.SunCertPathBuilderException: 
unable to find valid certification path to requested target

The root certificates (and intermediate certificates) are available here:
https://www.startssl.com/certs/



Kind regards,
Lennard Warnaar