ASP.NET 4.0 application error: Unrecognized attribute 'targetFramework'

You may experience the following error when you attempt to open your web application:
Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.

Parser Error Message: Unrecognized attribute 'targetFramework'. Note that attribute names are case-sensitive.

The error indicates that your account is configured to run with an ASP.NET framework version that may not match your application framework.

To resolve the problem simply go to the ASP.NET Version page in Control Panel to switch the framework.