Server storage of Cookies

As described previously a Cookie: header is sent from a browser to a web server. The web server may immediately use the information to customize content to the requesting browser, but it will also usually log the fact that it received such a request in its server log files with other standard information. Such a logging event usually looks as follows: - guest [4/Aug/2010:13:55:36 -0700] "GET /showtimes/results.html HTTP/1.0" 200 19743 "zip=90210"

Decoding this, what it really says is that IP address, logged in to the server as "guest", requested the page /showtimes/results.html on August 4th, 2010 at 1:55pm. The numbers at the end, 200 and 19743 are the return code and the page size respectively. 200 here indicates that the pages was successfully returned (please see the w3 site for a full listing of possible return codes) and 19743 means that the size of the page returned was 19743 bytes.

By logging this type of data, the site is able to gather metrics like, "how many of the people coming to my results page were from a California zip code".

Please note this is a simple and straight forward example of the type of meaning that can be derived. We will go into further detail in a later section.