An expert system Web interface to CS Stores called E-Referencer is being developed to help users search library catalogs on the Internet more effectively. An initial prototype has been implemented. The interface encapsulates some of the knowledge and searching expertise of experienced librarians. It has a repertoire of initial search strategies and reformulation strategies that it selects and implements to help users retrieve relevant records. It uses the Z39.50 protocol to access library systems on the Internet. This paper describes the design of E-Referencer, and the development of search strategies to be used by the interface.