ASPNET: Parser Error Message: Unrecognized attribute 'targetFramework'.

Came across an annoying error this morning whilst deploying a custom web service onto a client machine.

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:

Line 10:   </connectionStrings>
Line 11:   <system.web>
Line 12:     <compilation debug="true" targetFramework="4.0">
Line 13:       <assemblies>
Line 14:         <add assembly="System.Design, Version=4.0.0.0, Culture=neutral, PublicKeyToken=F03F5F4F13D50A4B" />

The way to solve this is to check the framework of the application pool for the site as i had mine set to 2.0, changing this to 4.0 solved the problem immediately.

Thanks

Jonathan