Original sentence: The website uses Microsoft Silverlight as opposed to Flash (used by BBC iPlayer and Channel 4's 30 day catch-up service) and Windows Media Video (used by 4oD)
Edited sentence: An unofficial Firefox add-on has been created to remedy this problem for users who have problems with Silverlight, or do not use currently-supported platforms.The website uses Microsoft Silverlight as opposed to Flash (used by BBC iPlayer and Channel 4's 30 day catch-up service) and Windows Media Video