It indicates that you enable the yours IIS to need to enable windows authentication.
Follow the below steps it solve your problem.
Open IIS Manager (Internet Information Services)
- Right-click the web site (in case you run it locally you only have Default web site) and pick Properties.
- Choose “Directory Security” tab and click Edit on “Anonymous access and authentication control”
- In the opening window, uncheck “Allow Anonymous access” and check “Integrated Windows Authentication
Could not load file or assembly ‘Microsoft.Web.Extensions, Version=1.0.61025.0, Culture=neutral, ublicKeyToken=31bf3856ad364e35’ or one of its dependencies. The system cannot find the file specified.
In your application uses ajax extensions.But in it not installed.
Solution for the this problem just download ASPAJAXExtSetup.msi and install it will solved.
Note: If your using vs2005 download and install ASPAJAXExtSetup.msi 2.0
If your using vs2008 download and install ASPAJAXExtSetup.msi 3.5