Because the idea of a public-access authority is somewhat contrary to the idea of root-authorities and trust, it’s not going to be supported in any/many browsers. From Wikipedia:
Thus, for most web users, a certificate signed by CAcert behaves like a self-signed certificate.
Still, it’s a cute idea.
Image may be NSFW.
Clik here to view.
Image may be NSFW.Clik here to view.
