ASP.net 3.5 Windows Authentication Problems

I'm new to ASP.net and trying to set up an Intranet site with Windows Authentication.   
I have configured the web.config as shown below.
<authentication mode="Windows">
<roleManager enabled="true" />
I wanted to do authorization by roles so
<authorization>
          <deny users ="?"/>
          <allow roles="D820\MySite_Developers, D820\MySite_Admins"/>
      </authorization>

I'm in the D820\MySite_Developers group.
When I attempt to login, it wants my password.  I thought that wit ...