Abstract: A system and method for accurately tracking user activity and transactions on public and private networks. The invention tracks user identification information and transaction identification information to determine whether an affiliate has referred a user to a particular web site. When a user selects a merchant's banner from an affiliate web site, before redirecting the user's computer to the merchant's web site, information about the merchant's site is stored at the user's browser. This information is then sent from the user's browser to other network data stores and can be used to determine whether an affiliate has referred a user to a particular site.