• by Wendy Davis , Staff Writer @wendyndavis, October 26, 2012

Several weeks ago, the self-regulatory group Digital Advertising Alliance said that members wouldn't be required to honor do-not-track signals coming from users who surf the Web with Internet Explorer 10.

Today, Microsoft's search partner, Yahoo, took the DAA up on its offer. The company announced on its blog that it has no intention of honoring do-not-track signals from IE10 browsers.

Yahoo said it supports do not track "in principle," but that Microsoft's decision to activate the header "degrades the experience for the majority of users and makes it hard to deliver on our value proposition to them."

The company added: "Ultimately, we believe that DNT must map to user intent -- not to the intent of one browser creator, plug-in writer, or third-party software service. Therefore, although Yahoo! will continue to offer Ad Interest Manager and other tools, we will not recognize IE10’s default DNT signal on Yahoo! properties at this time."

All of the major browser companies now offer a do-not-track option, but Microsoft is the only one that has said it will turn the header on by default in some circumstances. Windows 8 offers users two choices at installation: "express settings," which include do-not-track by default, or "customized," which don't.

Do-not-track headers signal to publishers that users don't want to be tracked, but don't stop publishers or ad networks from collecting data or serving ads. Instead, it's up to  publishers and ad networks to decide how to respond to the request. The standards group World Wide Web Consortium is trying to forge a consensus about how to interpret do-not-track signals, but ad industry representatives, privacy advocates and computer scientists have been unable to agree.

Microsoft's decision infuriated the ad industry, largely because many people never change their default settings.

But Yahoo's announcement that it will ignore IE10 do-not-track requests means that IE10 users no longer have a browser-based do-not-track option -- even if those users would have explicitly activated the feature. Yes, as Yahoo says, those people still have other means of opting out of online behavioral advertising. But at this point it's not clear they'll even realize that Yahoo isn't honoring their do-not-track headers. After all, it's not as if every casual Web users scours corporate blogs, looking to see whether the companies intend to honor do-not-track requests.