Internet作为传输媒介的一个应用系统，WWW网上最基本的传输单位是Web网页。WWW的工作基于客户机/服务器计算模型，由Web 浏览器(客户机)和Web服务器(服务器)构成，两者之间采用超文本传送协议（HTTP）进行通信。HTTP协议是基于TCP/IP协议之上的协议，是Web浏览器和Web服务器之间的应用层协议，是通用的、无状态的、面向对象的协议。HTTP协议的作用原理包括四个步骤：-WWW Internet as a transmission medium is an application system, WWW Internet transmission unit is the basic Web page. WWW' s work is based on client/server computing model, by the Web browser (client) and Web server (server) constituted between the two using the Hypertext Transfer Protocol (HTTP) for communication. HTTP protocol is based on TCP/IP protocol on top of the protocol, the Web browser and a Web server application layer protocol that is generic, stateless, object-oriented protocol. The role of the HTTP protocol principle consists of four steps: