Asp.net form authentication redirection doesn't work on iis7

Hi ,
I'm using .net 4.0 and iis 7 and windows server 2008
my web application use form athentication and wok properly in vs 2010
but when i try to config the web site in iis 7 the form athenticate redirection doesn't work without any kinds of error.
here is my web.config code
<authentication mode="Forms">
      <forms loginUrl="Pages/login.aspx" name=".ASPXFORMSAUTH"></forms>
    </authentication>
    <authorization>
      <allow users="?" />
    </authorization>
I enabled the authentication form in iis.
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