The language of the World Wide Web is Hypertext Markup Language (HTML). The Hypertext Transfer Protocol (HTTP) is where the World Wide Web is based. HTTP is a stateless protocol, meaning it does not track information about successive communications. See the session tracking problem illustrated below.
Clicking a browser link sends a message to the server. The server responds by sending the document. Once the browser receives the entire document, the server no longer tracks the session.
This works well for requesting a static page from the server; however, HTTP is not sufficient to program a multiuser interactive application. For example, consider an interactive customer update application. The server must be able to store the current state of the progressing transaction between data transfers. The server, like any application, must not allow other users to update records that are currently locked. HTTP cannot accomplish this task by itself.
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