Cookies are blocks of text placed in a file on your computer's hard disk. Web sites use cookies to identify users who revisit their site. Cookies might contain login or registration information, "shopping cart" information or user preferences. When a server receives a browser request that includes a cookie, the server can use the information stored in the cookie to customise the web site for the user. Cookies can be used to gather more information about a user than would be possible without them.