You can read a three part series on this : https://www.eff.org/deeplinks/2009/09/new-cookie-technologies-harder-see-and-remove-wide https://www.eff.org/deeplink

You can read a three part series on this : https://www.eff.org/deeplinks/2009/09/new-cookie-technologies-harder-see-and-remove-wide https://www.eff.org/deeplinks/2009/09/new-cookie-technologie... In short: http://en.wikipedia.org/wiki/HTTP_cookie#Supercookie http://en.wikipedia.org/wiki/HTTP_cookie#Supercookie