A cookie server generates a public cookie which uniquely identifies a client and is adapted for the client to access multiple operator servers that are recognized by the public cookie. When an operator server receives an access request from the client without a valid public cookie recognizing the operator server, it redirects the access request to the cookie server, which generates a public cookie, redirects the access request back to the operator server and passes along the public cookie. The operator server then writes the public cookie into the client and binds itself with the public cookie. A public cookie may include a group of related cookies identifying the common client that are generated this way to allow the same client's activities to be tracked by different operator servers having different domain names over the Internet.