Yahoo slammed Microsoft today over its use of “Do Not Track” by default in Internet Explorer 10. This is interesting on several levels, but most notably because Yahoo and MIcrosoft are partners in search and advertising. Together, they have put together the Yahoo Bing Network. Perhaps you’ve heard of it.

This close relationship the two companies have developed in recent years (officially called a “search alliance”) has not stopped Yahoo from taking a public shot at its partner in a post on its Privacy blog (h/t: Kara Swisher).

“At Yahoo!, we aspire to make the world’s daily habits more inspiring and entertaining,” the post begins. “Our users have come to expect a personalized Yahoo! experience tailor-made for their lives — whether they’re checking local weather, sports scores, stock quotes, daily news, or viewing ads on our site. We fundamentally believe that the online experience is better when it is personalized.”

“That said, we also believe that there should be an easy and transparent way for users to express their privacy preferences to Yahoo!,” it continues. “That’s why we offer our own tools and resources such as Ad Interest Manager, to give users more control over personalized advertising on Yahoo!, and why we participate in industry-wide programs such as AdChoices, which allows users to learn why they’ve been shown an ad.”

Then the calling out begins.

“Yahoo! has been working with our partners in the Internet industry to come up with a standard that allows users to opt out of certain website analytics and ad targeting,” Yahoo says. “In principle, we support ‘Do Not Track’ (DNT). Unfortunately, because discussions have not yet resulted in a final standard for how to implement DNT, the current DNT signal can easily be abused. Recently, Microsoft unilaterally decided to turn on DNT in Internet Explorer 10 by default, rather than at users’ direction. In our view, this degrades the experience for the majority of users and makes it hard to deliver on our value proposition to them. It basically means that the DNT signal from IE10 doesn’t express user intent.” Emphasis ours.

“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,” says Yahoo. “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.

Partners can have disagreements and continue to work together, but you have to wonder if the relationship between these two companies is going south. There were already rumors going around that the their partnership might not last for its entire decade run.