Roles in membership not work

I have a folder /Admin. I don't want 
users in "User" role can access that folder but users in "Admin" role.
My web.config file is like below
  <location path="Admin">
    <system.web>
      <httpRuntime executionTimeout="340" maxRequestLength="20480" />
      <authorization>
        <allow roles="Admin"/>
        <deny roles="User" />
        <deny users="?"/>
      </authorization>
    </system.web>
  </location>
In that situation every user can access Admin folder. When I change the web.config like;
  <location path="Admin">
&nb ...