"www.cacert.org uses an invalid security certificate. The certificate is not trusted because no issuer chain was provided. (Error code: sec_error_unknown_issuer)" (with Firefox)

May want to fix your own site's certificate acceptance before issuing to others.

If you want free certs go to startssl.com.

I appreciate Cacert's initiative, but they've been at it for years now and there is still not proper support in the mainstream browsers/platforms.