Platform for Privacy Preferences

The Platform for Privacy Preferences (P3P) is a specification and vocabulary that enables Web sites to communicate their data management practices to Web site visitors in a machine-readable format. P3P enables Web sites to translate their privacy practices into a standardized, machine-readable format (Extensible Markup Language - XML) that can be retrieved automatically and easily interpreted by a user's browser

P3P was developed by the World Wide Web Consortium (W3C), an organization created in October 1994 to lead the World Wide Web to its full potential by developing common protocols that promote its evolution and ensure its interoperability.
The W3C has more than 500 member organizations from around the world and has earned international recognition for its contributions to the growth of the Web.

If you want to implement P3P you can follow this implementation guide and this is a guide to help organizations incorporate the Platform for Privacy Preferences (P3P) into their Web site(s)