1. A method for referring an advertisement from a first user device to a second user device, the method comprising: receiving a first notification from a first user device that the advertisement is to be referred to at least the second user device; storing information associated with the first user device and information associated with the advertisement; and if the second user device accesses the advertisement, then: receiving a second notification from the second user device that the advertisement was accessed, and storing information associated with the second user device and information associated with the advertisement.