How to fix it
There are two ways to fix this issue. The first is to just disable BrowserLink in Visual Studio. In the toolbar, you can click the BrowserLink dropdown and uncheck "Enable Browser Link". Another option is to fix it per project. This is my preferred method since it only needs done for projects using our controls, and it can also be applied to many machines by adding it to Source Control. To disable BrowserLink for a single project, simple add the following to your web.config file.
<appSettings> <add key="vs:EnableBrowserLink" value="false" /> </appSettings>
After applying either fix, just run your application again and everything should be OK. Make sure to clear your browser cache too. Notice that all of the HTTP Requests to embedded resources are not returning the correct content. Microsoft is aware of the issue and has reported it fixed. We are all looking forward to the next release so that our Controls are not broken out of the box in Visual Studio.