We have identified an issue affecting newer browsers and certain sites using frames, where the domain of the master frameset URL does not match the domain of individual content page URLs displayed inside that frameset.
E.g., if you are using a site-builder service that hosts your actual, individual pages at something like this:
...but you are displaying those individual pages inside a frameset "wrapper" page with a URL on your own custom domain, so that a visitor's browser only shows the site's Web address as:
Modern browsers such as Internet Explorer v7.x, Apple Safari v3.x, and the new Firefox v3.x have increasingly added an option to "Block 3rd party cookies" or "Only accept cookies from sites I navigate to directly"; Safari even makes this the default setting, whereas the other browsers optionally allow the user to put that setting into effect. Our standard cart always sets the buyer's cart-tracker cookie as a "first party cookie" with the same domain as your page which contains our View Cart button code; however, if the URL of the page itself has one domain, but the Web address visible in the browser's address bar has a different domain (because of a frameset wrapper), then newer browsers will treat that as a third-party cookie (just as if it were a banner ad displayed in an IFRAME).