web.config, Forms-Based Authentication - newbie spørgsmål

Hey.. jeg har et lille problem med en web.config fil.

Jeg har "lånt" koden fra http://www.dotnetjunkies.com/quickstart/util/srcview.aspx?path=/quickstart/aspplus/samples/security/CookieAuth/cookieauth.src&file=CS\web.config&font=3  til at lave formbaseret sikkerhed med:
----
<configuration>
  <system.web>
      <authentication mode="Forms">
        <forms name=".ASPXUSERDEMO" loginUrl="login.aspx" protection="All" timeout="60" />
      </authentication>
      <authorization>
        <deny users="?" />
      </authorization>
    <globalization requestEncoding="UTF-8" responseEncoding="UTF-8" />
  </system.web>
</configuration>
----

Det virker fint, lige indtil jeg selv retter lidt i kode for at lave sikkerheden på et under-bibliotek (testbib), istedet for rod-biblioteket ved at gøre følgende:

---- med min tilhøjelse af <location> --
<configuration>
<location path="testbib">
  <system.web>
      <authentication mode="Forms">
        <forms name=".ASPXUSERDEMO" loginUrl="login.aspx" protection="All" timeout="60" />
      </authentication>
      <authorization>
        <deny users="?" />
      </authorization>
    <globalization requestEncoding="UTF-8" responseEncoding="UTF-8" />
  </system.web>
</location>
</configuration>
----

Når jeg så retter min browser i mod en fil i underbiblioteket "testbib" får jeg følgende fejl :

-----
Server Error in '/test' Application.

Configuration Error
Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.

Parser Error Message: It is an error to use a section registered as allowDefinition='MachineToApplication' beyond application level. This error can be caused by a virtual directory not being configured as an application in IIS.

Source Error:


Line 2:  <location path="testbib">
Line 3:    <system.web>
Line 4:        <authentication mode="Forms">
Line 5:          <forms name=".ASPXUSERDEMO" loginUrl="testbib/login.aspx" protection="All" timeout="60" />
Line 6:        </authentication>


Source File: C:\Inetpub\wwwroot\Test\web.config    Line: 4
-----

Hvad er det så jeg har misforstået med hensyn til <location path="testbib"> i min web.config fil ?

hilfe plz ;o)