There’s a new online location for all the certification authorities (CAs) and corresponding root certificates that come pre-installed on Windows Phone devices. CAs vouch for the identity of users who hold certificates, which enable secure communications with websites and services. This information is available on MSDN at: http://msdn.microsoft.com/en-us/library/gg521150(v=VS.92).aspx
MSDN will continue to host this information in the future. For an interim period, it will also remain available in the “Windows Phone 7 root certificates” article on the Windows Phone 7 Guides for IT Professionals page on the Microsoft Download Center.