Hypertext Transfer Protocol (HTTP) is a stateless protocol. To say it in a simple way: A client (web browser) connects to a web server, sends a request, and gets a response. Then, the connection is closed. The consequence is the next time the same client sends a request to the same web server, it is a new request, so the web server cannot identify the caller. This is, of course, a problem for applications in which state must be maintained, for instance e-commerce applications with a shopping-cart functionality. | 
