The Windows team has published an updated version of the Windows Phone 7 application certification requirements, which can be found on the AppHub.
The release is part of efforts to make the certification process as clear, transparent, and efficient as possible for developers.
Changes include trimming the maximum package size from 400 to 225 MB, and added information about the Windows Phone capability detection tool.
There is also a revision on requirement to describe that screenshots must not include any emulator chrome
.