Information retrieval has expanded beyond its traditional home in libraries and formal information systems; it is now firmly in the hands of end-users. Contemporary information systems must fit themselves to the universal WWW browser interface, and customers quickly move from one system for another if the first does not deliver the right results. In this model of information retrieval, the end-user is customer and king. Today's information retrieval systems usually have interfaces that are so simple and so similar that new customers can rapidly teach themselves how to use most of the system. These changes are most completely developed in the Internet search engines.