500.19 - Internal Server Error

 The requested page cannot be accessed because the related  configuration data for the page is invalid.

500.19 - Internal Server Error - The requested page cannot be accessed because the related configuration data for the page is invalid..

if we get error like above we can add below lines in web.config file 
 Unsubscribe.aspx--> accessing page in my scenario.
<location path="Unsubscribe.aspx">
    <system.web>
      <authorization>
        <allow users="*"/>
      </authorization>
    </system.web>
  </location>