Cookies also provide the means to track users. Servers can log which sites users previously visited. In essence, a user's past, present, and future navigation can be tracked. Advertisers can track how often the user hits a site, how long they remain at that site, which advertisements or links are of interest, and at what point the user loses interest and leaves the site. The data gathered can be used to customize sites.
Marketers predict age, sex, and household income based on behavior observed via cookies.
With this information they can provide advertisements, services, etc that are relevant to the customer. Dead ends at a site can be filled with information that pertains to the behavior and interests of the user. Site tracking and customization is analogous to ordering a car. When negotiations are complete, the customer receives a custom ordered vehicle. Like a car, sites can be customized based on habits and interests.