Start Action indicates the item to start when the Silverlight application is debugged: a dynamically generated Web page, or a specified Web page.
Dynamically generate a test page
Select this option if you want to generate a test page as part of the build process into the output folder. The project will use this generated test page to host your application when you debug the project, or when you run the project without debugging.
Select this option to specify a page that you have added to your project to host your application. This page will be used when you debug the project, or when you run the project without debugging.
Select this option to specify the Silverlight application that you want to run outside the browser. For more information see Out-of-Browser Support topic.
This option is enabled if you select the Enable running application out of the browser check box in the Silverlight page of the Project Designer.