I've been reading about some people using "Refer a friend" scripts on their "Thank you" page after a user signs up to their list. I guess they use a script to track referrals in order to give them an additional free bonus.
Does anyone have any idea which script would be good for this? One that, I presume, tracks referrals from an individual before it "unlocks" the free bonus for them.
Any ideas? Or have I misunderstood the functionality of such a script.