Only persistent cookies can be used to track a user at more than one site. Setting the date for an existing cookie to be some day in the past deletes the cookie. This allows larger web sites to coordinate multiple servers in the same subdomain. Three dots are required for any other domain. This is to prevent the subdomain from being set to something like .COM, the subdomain of all commercial machines.
PATH is an attribute that is used to further refine when a cookie is sent back to a server.
When a browser sends a request to a server, it includes its IP address, the type of browser you are using, and the operating system of your computer. This information is usually logged in the server's log file. A cookie sent along with the request can add only that information, which is contained in the cookie and which, was originally sent to the browser by the same server. Thus, there is no additional personal information explicitly sent to the server by allowing cookies. As mentioned above, cookies are used by Internet shopping sites to keep track of you and your shopping cart.