(Solved) Error: Unrecognized attribute 'targetFramework'.

Error:

Configuration Error

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.

Source Error:

</controls>  
    </pages>  
    <compilation debug="true" targetFramework="4.0" />    
<authentication mode="Forms">  

Solution:
In IIS 5.1

• Go to Start -> Run
• Type "inetmgr" then press Enter
• In the Default Web Site right click your web application then select Properties
• Navigate to ASP.NET tab
• Change the ASP.NET version to 4.0
• Press Apply
• It will work now