If you have more than one site, you can track visitors going from site to site. You do this by displaying an image on all pages of each of your sites, an image that is retrieved from one common domain via CGI or other method that sets and retrieves cookies and also maintains auxiliary databases on its server. The image can be a banner, a 1x1 pixel GIF, or any other image. Many banner dispensing domains use cookies this way. This method of using cookies can be a privacy infringement if the data thus obtained is collated with other sources of information.
People sometimes share computers.
Some people use more than one computer. Some browsers are set to reject cookies. Cookies can be erased. Still, using cookies is the most efficient method of remembering and tracking. Part 2 Now you will find how to implement JavaScript cookie code on your site.