From what I have heard second-hand is that there are different development teams inside Microsoft that develop different versions of IE for different platforms. For example, there's one team that works on the browser on the Zune and another that works on IE9. There might be others, but I'm not sure. 

Further, it seems that each team is working on its own code version for IE. The Zune team deployed a version of IE6 based on a code base that was outdated by more than 5 years. Meanwhile, the other team is working on IE9.

There seems to be very little communication between internal teams that are more or less working on the same project.

I would like to ask, when will Microsoft settle on making one version of their browser for both desktop and mobile? The first example I can refer to is Safari. Safari on the desktop and on the iPhone are based on the same rendering and javascript engines. The UI layer is different, depending on the platform its deployed to, but the stuff underneath is unified.

With the exception of Mozilla and Microsoft, all the popular browsers these days are using Webkit. Improvements from various venders are routinely pulled in. The rendering of pages is made mostly universal between Webkit-based browsers. Meanwhile, each vendor is iterating fiercely with javascript engines and css extensions. I love the gpu enhanced CSS animations in Safari, even though Chrome doesn't support all of them. 

I doubt that Microsoft would ever adopt Webkit. I'm not even sure if its a good idea. But at least internally, it would be very, very useful if there was only one browser that Microsoft developed. Have the core team working on the DOM and javascript engines, then share that code between various sub projects like desktop IE and mobile IE.

If this strategy was adopted, then I can easily imagine Microsoft releasing browsers for Android, iPhone, and Mac OS. If they are fast, render properly, and really compete against the other vendors then its only good for everyone.