Also still up in the air is what websites and advertisers will be bound to do when they recognize IE10, assuming Microsoft does not change its mind on DNT and the default setting it has planned.

"We don't have agreement on what the ramifications are. Can ad networks ignore a tracking request from IE10?" Mayer said. "Google and Yahoo and Adobe said they should be able to ignore the header from IE10, but Mozilla and Apple have said that ad networks should not ignore it."

Microsoft was not available for comment on the W3C draft specification that would bar it from advertising IE10 as compliant with DNT.

Mozilla also did not reply to questions related to the ongoing discussions of the W3C group.

Microsoft has not said when it will ship a final version of IE10 -- apparently that will not happen until Windows 8 launches later this year -- but enabled the DNT signal with the sixth early build of the browser that was bundled with Windows 8 Release Preview. That today and is available for free downloading from .