The user gets a warning saying that site identity could not be verified and the user can add an exception if they want.
Those are SSL Cert warnings. You will get to get a signed cert to avoid them.
SSL Certs are pretty cheap now.
http://startssl.org will generate certs for free but you have to register and jump through a few hoops.
Neil
-- Neil Aggarwal, (281)846-8957, http://UnmeteredVPS.net/centos CentOS 5.4 VPS with unmetered bandwidth only $25/month! No overage charges, 7 day free trial, PayPal, Google Checkout