[O] orc-contacts contacting ww.gravatar.com! -- How to switch off?

[AW]

Hi,

I'm exploring the org-contacts. When I do M-x org-contacts, Emacs tries to 
contact www.gravatar.com:80

How can I switch that off?

Besides that, what I really miss is a comprehensive manual on org-contact. OK, 
I can search for a name as described above, I can add a new contact with M-x 
org-capture, but what else?

Thank you,

Regards,

Alexander