Suppose you want to provide a service to users, to which the user can connect either anonymously or non-anonymously, and the user can switch back and forward between these services withour having to login again. To achieve this you want to use different cookies for these two uses. How can this be achieved?
Cookies are limited to a specific domain name. By using different domain names for the anonymous and non-anonymous service, they will have different cookies, so that a user can switch between using the anonymous and the non-anonymous service without having to specify a login name and password more than once.
Example: Use anon.foo.bar as the domain name for anonymous ratings, and non-anon.foo.bar as the domain name for non-anonymous ratings. Both domain names can still refer to the same physical server host.
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