What about "cookies"?
"Cookies" are small pieces of state information which are stored by your browser on your computer's hard drive. Cookies send information to your browser and for the browser to return the state information to the origin site. The state information can be used for authentication, identification of a user session, user's preferences, shopping cart contents. Cookies are not software. They cannot be programmed, cannot carry viruses, and cannot install malware on the host computer.