x-mozilla properties

Hi!

    I would like to know about x-mozilla vCard properties, exactly=20
x-mozilla-html and x-mozilla-cpt. What is their purpose or their origin?=20
I thought that neither Netscape nor Mozilla supported vCard before=20
Mozilla 1.6, released in January so, it seems very extrange that=20
Netscape or Mozilla could define any vCard extension.

Any help would be appreciated.
Thank you,
Germ=E1n.