Faking Referrer To A Gateway

Anyone know how or tried to fake the referrer so it looks like its coming from a page with a gateway?

To them does it look like the traffic comes from the little gateway thing, a js script or the normal page being gatewayed as if it was a text link on that page?

Also, what about faking a whole gateway. So using a gateway provided by someone else, but making it look like its on a different site than it is.

Thanks people