Cookies of domain are sent to subdomain, how to fix?

Firefox is sending my ".domain.tld" cookies when I go to sub.domain.tld.

How can I make sure that the browser only sends co开发者_如何学Gookies of ".sub.domain.tld" and not ".domain.tld"?

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You cannot. If you set a cookie on .domain.tld it will be sent to domain.tld and all subdomains.

Although this may be unrelated to your problem, take a look at sstatic.net - where the Stack Overflow family of sites host their static resources.