The present server based communications system provides dynamic customization of hypertext tagged documents presented to clients accessing the system. The customization, which pertains to the content of the documents, is based on the specific requirements of a class to which the client belongs to. The class may be defined by the identity of the source which refers the client to the system. The system utilizes a database which dynamically retrieves stored data in response to a server software tool which configures the data into hypertext tagged documents. The system utilizes a dynamic token scheme to pass the identity of the referring network site from document to document to eventual purchase document accessed by the client through the hypertext tags.