One-to-one marketing on the Web is in its infancy. The Web offers a unique opportunity to mass market products directly to potential buyers who have a high probability for purchase, and to do so at a low cost. The key to unleashing this potential is the tailoring of Web presentation to address individual needs and desires quickly. This capability requires a mechanism for change so the site can adapt to the user. It also requires the ability to store and quickly access databases. We believe that an expert system is uniquely capable of providing this ability.