cannot read configuration file due to insufficient permissions

 Apply the following cnhages in IIS7.

1.In Windows Explorer, locate the web.config file that is associated with the Web site.
2.Right-click the web.config file
3.Click Properties.
4.Click the Security tab, and then click Edit.
5.Click Add.
6.In the Enter the object names to select box, type computername\IIS_IUSRS, click Check Names, and then click OK.
Note Computername is a placeholder for the computer name.
7.Click to select the Read check box, and then click OK.
8.In the Web.config Properties dialog box, click OK.