Cookies ExplainedThe WWW is built on a very simple, but powerful premise.
All material on the Web is formatted in a general, uniform format called HTML (Hypertext Markup Language), and all information requests and responses conform to a similarly standard protocol. When someone accesses a server on the Web, such as the Library of Congress, the user's Web browser will send an information request to the Library of Congress' computer. This computer is called a Web server. The Web server will respond to the request by transmitting the desired information to the user's computer. There, the user's browser will display the received information on the user's screen.
Cookies are pieces of information generated by a Web server and stored in the user's computer, ready for future access. Cookies are embedded in the HTML information flowing back and forth between the user's computer and the servers. Cookies were implemented to allow user-side customisation of Web information. For example, cookies are used to personalise Web search engines, to allow users to participate in WWW-wide contests (but only once!), and to store shopping lists of items a user has selected while browsing through a virtual shopping mall.
Essentially, cookies make use of user-specific information transmitted by the Web server onto the user's computer so that the information might be available for later access by itself or other servers. In most cases, not only does the storage of personal information into a cookie go unnoticed, so does access to it. Web servers automatically gain access to relevant cookies whenever the user establishes a connection to them, usually in the form of Web requests.
Cookies are based on a two-stage process. First the cookie is stored in the user's computer without their consent or knowledge. For example, with customisable Web search engines like My Yahoo!, a user selects categories of interest from the Web page. The Web server then creates a specific cookie, which is essentially a tagged string of text containing the user's preferences, and it transmits this cookie to the user's computer. The user's Web browser, if cookie-savvy, receives the cookie and stores it in a special file called a cookie list. This happens without any notification or user consent. As a result, personal information (in this case the user's category preferences) is formatted by the Web server, transmitted, and saved by the user's computer.
During the second stage, the cookie is clandestinely and automatically transferred from the user's machine to a Web server. Whenever a user directs her Web browser to display a certain Web page from the server, the browser will, without the user's knowledge, transmit the cookie containing personal information to the Web server.
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