Here's the HTML5 test report from the Windows Phone 8 emulator, which has Internet Explorer 10 Mobile. As a web developer, I'd like to remind everyone that this is just a number, and gives no details about the quality of the implemented features, or the impact of their lacking on the end user. For example, file uploads (cough) are still not supported, and device sensor data is unavailable to the browser. This prevents any rich, intuitive web applications from being developed.

But for those who were curious, here you have it. Major point deductions were form inputs (no date time selector, etc) and touch/sensor data APIs. More information on the Windows Phone 8 emulator.