Authorization users

Hello,
in my web.config I have following:
 <identity
   impersonate="true"
      userName="Domain\CustomASP"
      password="blabla!"   />

  <authentication mode="Windows">
  <authorization>
      <allow users="*"/>
  </authorization>
I can access the main page without any problems on my webserver but when I want to load the page on a client, it always shows a login box. I can't login without any login (also administrators). And after a while it shows:
You are not authorized to view this pageYou do not have permission to view this directory or page using the credentials that you supplied. Please try the following:
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