В "неубиваемых куках" упомянуты "куки" в ETags, дял которых не нужен JS:
Цитата:
http://en.wikipedia.org/wiki/HTTP_ETag
Tracking using ETags
ETags can be used to track unique users,[2] as HTTP cookies are increasingly deleted by privacy-aware users. As of July 2011, researchers report that a number of Websites, including Hulu.com, are using ETags for tracking purposes.[3] Hulu and KISSmetrics have both ceased "respawning" as of 29 July 2011,[4] as KISSmetrics and over 20 of its clients are facing a class-action lawsuit over the use of "undeletable" tracking cookies partially involving the use of ETags.[5]
Because ETags are cached by the browser, and returned with subsequent requests for the same resource, a tracking server can simply repeat any ETag received from the browser to ensure an assigned ETag persists indefinitely (in a similar way to persistent cookies).
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Вот только для типового сценария голосования не подходит. Так как ETag однозначно связан с URL. А URL голосования обычным GET/POST или AJAX отличается от URL исходной страницы. Значит броузер ETag не передаст при голосовании. Таким методом можно отслеживать уникальные и повторные посещения обычных страниц сайта.