401 Unauthorized error web api mvc windows authentication

asp.net-web-api, c#, http-status-code-401, iis-7

Solution

I added below lines in web config to fix the issue and it worked.

   <security>
        <authorization>
            <add accessType="Allow" users="*" />
        </authorization>
    </security>

Problem

I am getting 401 unauthorized error . My web service is written in mvc . in IIS configured to use windows authentication. Below is screen shot of fiddler When I hit URL from browser it gives me popup window to enter user name and password. How can I avoid popup window? I am calling this web api from another window service.

Original source