A method and system of generating a user profile for advertisement over a computer network is disclosed. A webpage identifier that identifies a webpage and a content category identifier that identifies a content category is generated. The webpage identifier is associated with the content category identifier if web content depicted in the webpage is relevant to the content category. A web server then receives a request for the webpage including the webpage identifier and a first user identifier from a client computer connected to the computer network. A user profile is located by determining whether the first user identifier matches a second user identifier corresponding to the user profile. The user profile includes at least one user content category identifier and a corresponding user interest score. The corresponding user interest score is increased by the predetermined amount if the content category identifier matches the user content category identifier.