Université Catholique de Louvain: Olivier Bonaventure's "Computer Networking: Principles, Protocols, and Practice"
Read Section 3.2.3, "HyperText Transfer Protocol," on pages 46-55. HTTP is a text-based protocol, in which the client sends a request and the server returns a response. In this section link across the World Wide Web via your textbook to see how this is accomplished.