Unrecognized Tag Prefix Or Device Filter In Visual Studio 2012

Today i am working on some project in ASP.NET, i am using Visual Studio 2012.On that i am stuck when i am using a LINKBUTTON there, but i am getting an error that Unrecognized Tag Prefix Or Device Filter In Visual Studio 2012.I searched on Google and MSDN forms but got nothing at all, after 2-3 hours of researched i found solution for that.

Solutions: 

1. Open your WEB.CONFIG

2. Delete these files from your web.config file.

<pages>
    <controls>
    <add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
    <add tagPrefix="asp" namespace="System.Web.UI.WebControls" assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
   </controls>
</pages>