It shows, among other things, the kind of browser software you are using, the kind of monitor, the additional plug-in programs that are installed. Most important, it shows a number called an IP address that is the steppingstone to finding out a slew of other details. If you are logging in from home, the IP address might point to an Internet service provider, whose geographic location might be indicated in a directory. Additional issues arise with cookies. While browser programs allow consumers to block cookies, that option sometimes makes it difficult to use features on some sites.
Cookies are most worrisome when they are placed by companies with connections to multiple sites.
These companies include those that distribute banner advertising around the Web. Each time a user calls up a Web page with one of those ads, the advertising distributor places its own cookie on the visitor's hard drive. Prying Eyes Networks that provide banner ads on the Web can track users, not only on a single site but across many sites. A banner-ad network establishes relationships with a number of Web sites that carry ads. Each Web site downloads the ads from the server machines run by the network.