I was working on an application which uses Telerik controls. The application was working fine for a while. Suddenly, the application stopped working. I mean lot of my application pages becoming very very ugly. I found JavaScript errors on every Browser's console. When I check the page view-source, the generated HTML was messy and invalid. This was only happening with my local machine. If someone else on my network accesses my application pages, he will get the correct HTML and no JavaScript errors. My mind was blowing because the same page was generating invalid HTML(and JavaScript errors) when I access the page using a local browser but generate correct HTML(and no JavaScript errors) when someone else access my application page remotely. Then I realized that I the only change I made last was opening my application in Visual Studio 2013 RTM which I installed few days ago. I closed the Visual Studio 2013, everything work like a charm. Then I became100% sure that this is only happening due to new Visual Studio 2013 feature called Browser Link. I just open the application again and add this in web.config. Everything become fine Happy coding :)

     <add key="vs:EnableBrowserLink" value="false" />