People interact more and more with computers, and they also interact more and more with different kinds of computers. While desktop and laptop computers may have been the most prevalent computers in people's lives in the past, more people now use mobile computers such as in the form of smart phones, and frequently use them without even thinking of them as being computers.
Users of mobile devices are now able to leave their other computers behind and to interact entirely on-line using their mobile computing devices. For example, music may be purchased on-line from music stores, and software applications can be purchased from application marketplaces. Both can then be downloaded and accessed immediately from the user's mobile device.
Developers of such electronic content, like sellers of any product, often prefer to advertise the content so as to make users aware of it and facilitate sales. Thus, they may run advertisements in various forms, where selecting the advertisement takes a user to a store where the user can buy the electronic content. Such developers may want to know when an ad is successful in creating a conversion (i.e., a purchase of content), or may want to pay for the ad only when it is successful in creating a conversion. However, there can be difficulties in determining how a user reacts to an ad when, in response to selecting the ad, the user is taken to a content store that is operated by an organization that is different than the organization that served the ad. In some circumstances, an IP address for a user may be checked, but wireless carriers often cause many different users to show the same IP address.