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Cookies give a Web site a way to track a user's patterns and preferences. A cookie is a piece of text that a web server can store on a user's hard disk. Cookies allow a web site to store information on a user's machine and later retrieve it. The pieces of information are stored as name-value pairs. For example, I have visited goto.com, and the site has placed a cookie on my machine. The cookie file for goto.com contains the following information: UserID A9A3BECE0563982D
What goto.com has done is stored on my machine a single name-value pair. The name of the pair is UserID, and the value is A9A3BECE0563982D. The first time I visited goto.com, the site assigned me a unique ID value and stored it on my machine. [Note that there probably are several other values stored in the file after the three shown above. That is housekeeping information for the browser.] Amazon.com stores a bit more information on my machine. When I look at the cookie file Amazon has created on my machine, it contains the following:
session-id-time 954242000 amazon.com/
session-id 002-4135256-7625846 amazon.com/ ubid-main 077-9263437-9645324 amazon.com/ It appears that Amazon stores a main user ID, an ID for each session, and the time the session started on my machine (as well as an x-main value, which could be anything). The vast majority of sites store just one piece of information -- a user ID -- on your machine. But there really is no limit -- a site can store as many name-value pairs as it likes. With the help of a browser, cookies are stored on the user's own hard disk. However, you can have your browser disable cookies or warn you before accepting a cookie. This is done in the cookie options in your browser in the Options or Preferences menu. Also there are a number of utilities that help you to crush (automatically refuse), manage, get rid of, and monitor cookie activity. These utilities have various names, such as "crusher," "cruncher," "wipe," and "terminator." |