The major configuration elements in ASP.NET 4.0 are moved to the machine.config file. Now, the applications are inheritting these settings.
The advantage of this setting is that, the web.config file in ASP.NET 4 applications to be empty or to specify only which version of the framework the application is targeting.
This can be seen clearly in the below example.
< ? xml version="1.0" ? >
< configuration >
< system.web >
< compilation targetFramework="4.0" / >
< / system.web >
< / configuration >