Read original post by Cheryl Simmons at Silverlight and Windows Phone SDK Blog
It was recently brought to my attention that we have done a poor job of evangelizing the Windows Phone Design Guidelines on MSDN. These guidelines were previously available in PDF format, but a few months ago a couple of folks worked really hard to bring these to MSDN. Given the success of one of my previous posts, the design cheat sheet, I would guess that developers are looking for these design guidelines presented in an easy-to-consume format.