Unrecognized attribute ‘targetFramework’.

Some times we receive the following error message when trying to run a .NET 4.0 or 4.5 application:

 

Unrecognized attribute ‘targetFramework’.

 
Error message
 

The cause is normally the application pool configure to run .NET 2.0 application.
 
In order to solve it, go to the application pool for your site and change it to run on .NET 4.0.
 
See you,
Amadeu.