One embodiment of the present invention provides a system that facilitates marking content during distribution of the content to a client. The system starts by receiving a request for the content from the client at the server and then obtaining a content identifier for the content. Next, the server generates a version identifier that uniquely identifies the version of the content that is sent to the client. Once the version identifier has been generated, the server stores the version identifier in a database along with information to facilitate identification of the requesting client. Finally, the server creates the version of the content by marking the content with the version identifier and delivers the version to the client. Note that the markings on the content facilitate subsequent identification of the client by examining the version of the content.