This is the same problem I had two days ago and it took me way too long to figure out. If you right click the project in Visual Studio and go to Property Pages you will see the targeted framework. You have said that your's is targeted correctly however under MSBuild Options make sure that you do not have any of the checkboxes checked. It took me forever to figure out that I had one checked off and it was interfering with testing in the browser. Hope this helps.