After createing a new ASP.NET application, and after publishing to certain folder, IIS7 refused to open the published site because of 500.19 error, IIS7 said that the requested page cannot be accessed because the related configuration data for the page is invalid.
But, in fact it is a security issues that prevent mister IIS7 from accessing web.config file. Particularly, it was computername\IIS_IUSRS that must take some permisions, read this article for more information.
Simply add the following groups into security tab to solve this problem:
1- Authenticated Users
2- Users (computername\Users)