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I was perusing my cookies, and discovered several cookies from various different sites, which all have the same value. They are all named "_csuid". I have another set, all from different sites, all with the same value, named "__qsa". It seemed rather strange that they would all be identical, despite coming from different sites.

In case it's relevant, I'm browsing with Camino on Leopard.

Does anyone know what these cookies are recording, since they appear to be tracking me across domains...?

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Do you mean __qca? I can't find anything about __qsa. – jtbandes Aug 2 '09 at 5:56

It appears that _csuid is from AddThis, and __qca and __qcb from Quantcast. Also, to my knowledge, the __utm* cookies are from Google Analytics.

Here's some good information on the Google Analytics cookies. It appears AddThis and Quantcast haven't published anything like that.

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