Deploying Silverlight is relatively easy, there are a few things which can be annoyances especially when using ria services as noted in my post https://refactorthis.wordpress.com/2010/11/23/deploying-silverlight-wcf-ria-services-on-iis-6/
To allow IIS to serve Silverlight content you will want to create a virtual directory containing your silverlight hosting web application. Ensure that your silverlight xap file is in the ClientBin. If it is not
Create your virtual directory and create a .NET application for it if it already doesn’t show up in IIS as an application.
Once at this point (the normal asp.net website deployment) we need to register the silverlight mime types. Right click on the virtual directory and go into the properties. Next head over to the ‘HTTP Headers’ tab and click on the ‘Mime Types..’ button. Here you will need to add 3 types to be sure.