In the World Wide Web, a computer "cookie" is a small piece of data that a web server sends to an Internet user's computer along with the requested web page. The web browser is supposed to save the cookie and send it together with all future requests to the same server (or group of servers). Although there are privacy and security concerns that cause some Internet users to block cookies, there is no danger that cookies will damage data on a user's computer or server; cookies cannot contain viruses since they are not executable files.

When a user clicks on a hyperlink, the browser sends a request to the web server specified in the Uniform Resource Locator (URL) underlying the hyperlink. The formal syntax for such requests and the corresponding answer (response) is regulated by the Hypertext Transfer Protocol (HTTP). For performance reasons, HTTP...