So, you load your Silver light application and get excited to view it for the first time on your web server. Boom!
You get a blank screen. Or if you have debugging enabled, you get an error trying to load Silverlight application file. hmmmm. What can this be?
Try typing in the direct url for the xap file on your server and you get “The request is not supported”.
It turns out it is simply the MIME type for XAP not being registered. Register it on your IIS server and problem solved.