You get :
500 - Internal server error
because your web.config file is set to use ASP.NET 3.5 while IIS8.0 offers ASP.NET 4.5.
There is a difference between web.config file for ASP.NET 3.5 and the new ASP.NET 4.5.
The workaround for the second scenario is to delete or comment out all the system.web.extensions configuration section definitions and configuration section group definitions from the application-level Web.config file. These definitions are usually at the top of the application-level Web.config file and can be identified by the configSections element and its children.
Also manually delete the system.codedom section, although this is not required.
Last update: 2012-10-15 10:17