This hotfix makes a new application setting available in ASP.NET 2.0. The new application setting is ‘aspnet:AllowAnonymousImpersonation‘. You can enable this setting by adding the following section to the Web.config file:

    <appSettings>        

<add key="aspnet:AllowAnonymousImpersonation" value="http://www.mamicode.com/true" />    

</appSettings>

To enable this setting, you must have IIS 7 or IIS 7.5 running in Integrated mode. When this setting is enabled, the application runs under the security context of the IUSR identity. Additionally, creating a Forms-based Authentication Web Application will enable the setting and set it to true.

({i:0#.w|nt authority\iusr})Sharepoint impersonates the IUSR account and is denied access to resources