In May, Barry reported that MSN adCenter would be offering an accreditation program. At this time, it's only available in beta to customers residing in the US, according to adCenterEU. By the end of this year, it will also be rolled out to UK customers.
The program is called adExcellence. US users interested in opting-in can sign up on the pilot program sign-up page.
Forum discussion at DigitalPoint Forums.