Cookies allow sites to keep track of users. Although not all sites use cookies, most major portal, e-commerce,
and advertising sites make extensive use of cookies.
Cookie technology has four componets: (1) a cookie header line in the HTTP response message; (2) a cookie header line
in the HTTP request message; (3) a cookie file kept on the user's end system and managed by the user's browser; (4) a back-end
database at the Web site.
Although cookies often simplify the Internet shopping experience for the user, they remain highly controversial because
they can also be considered as an infringement ona user's privacy.