authorization in .Net

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.NET

.NET4

I want to give rights to Active Directory group to access my site , I did the following change in my Web.config but it is not working.

What is the thing I m missing it here ? the changes in web.config are as follows:

<authentication mode="Windows">           
    </authentication>


<!-- This is change I did -->
    <authorization>
      <deny users="?"/>
      <allow roles="SupportPlan-Users"/>
    </authorization>



        <membership>
            <providers>
                <clear/>
                <add name="AspNetSqlMembershipProvider" type="System.Web.Security.SqlMembershipProvider" connectionStringName="ApplicationServices" enablePasswordRetrieval="false" enablePasswordReset="true" requiresQuestionAndAnswer="false" requiresUniqueEmail="false" maxInvalidPasswordAttempts="5" minRequiredPasswordLength="6" minRequiredNonalphanumericCharacters="0" passwordAttemptWindow="10" applicationName="/"/>
            </providers>
        </membership>
        <profile>
            <providers>
                <clear/>
                <add name="AspNetSqlProfileProvider" type="System.Web.Profile.SqlProfileProvider" connectionStringName="ApplicationServices" applicationName="/"/>
            </providers>
        </profile>
        <roleManager enabled="false">
            <providers>
                <clear/>
                <add name="AspNetSqlRoleProvider" type="System.Web.Security.SqlRoleProvider" connectionStringName="ApplicationServices" applicationName="/"/>
                <add name="AspNetWindowsTokenRoleProvider" type="System.Web.Security.WindowsTokenRoleProvider" applicationName="/"/>
            </providers>
        </roleManager>
    </system.web>
    <system.webServer>
        <modules runAllManagedModulesForAllRequests="true"/>
    </system.webServer>