Among other things, that helps them spot return visitors, how many times they return, and how they move around the site. That helps Webmasters sharpen their sites' appeal. Many Internet surfers repeatedly visit Web sites they have individualized to display information important to them. Some Webmasters control access to their sites, or to specific areas, by requiring the surfer to obtain a user ID and a password. These may also be stored in cookies to make it easier for regulars to gain faster access to the restricted areas.
Cookies can also contain other personal information, including the e-mail address of users.
But personal information winds up in a cookie only when users supply it themselves. No cookie has the power to roam all over a hard drive to collect personal information. Internet Explorer and Netscape can be configured to reject cookies. Check your browser's options and security menus for cookie-control measures. Doing so will make surfing difficult if not impossible.