Hosting ASP.NET in IIS7 gives Access is denied?

I have setup a application in my IIS7 that uses .NET Framework 4.0 (runned by NetworkService) but when browsing the site I get this:

Access is denied.
Description: An error occurred while accessing the resources required to serve this request. You might not have permission to view the requested resources.
Error message 401.3: You do not have permission to view this directory or page using the credentials you supplied (access denied due to Access Control Lists). Ask the Web server's administrator to give you access to*

I have tried to give NetworkService full permission on the folder that holds the website (the one that the web application in IIS is pointing against) but I do still get the access denied?

Why?

I gave access to "IIS_IUser" but instead it should be "IUSR". That solved the problem.

For me, nothing worked except the following, which solved the problem: open IIS, select the site, open Authentication (in the IIS section), right click Anonymous Authentication and select Edit, select Application Pool Identity.

I had the same problem, I enabled "Anonymous Authentication" but it still did not work. So I also ENABLED "Forms Authentication" Then it worked without any problems.