Ajaxcontroltoolkit - Unable to update auto-refresh reference

Problem - Warning: Unable to update auto-refresh reference 'ajaxcontroltoolkit.dll'. Cannot find assembly 'D:\Program Files\Microsoft ASP.NET\ASP.NET 2.0 AJAX Extensions\AjaxControlToolkit\Binaries\AjaxControlToolkit.dll'. Validating Web Site D:\ProjectFolder\Website\web.config(129): Build (web): Could not load file or assembly 'System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.


As I did a clean install of my O/S, I forgot to install Ajax Control Toolkit on my computer again. So just install the toolkit again on your computer from here http://ajaxcontroltoolkit.codeplex.com/ and update your .dll reference :)