I recently updated the Telerik controls on my ASP.NET web app (VS2013) and then got this message on the first compile:
It is an error to use a section registered as allowDefinition='MachineToApplication' beyond application level. This error can be caused by a virtual directory not being configured as an application in IIS.<
The problem is that I have my VS solution file (<proj>.suo) in the root directory of the web app. When I upgraded the project to the latest Telerik version, that caused the project backup to be created as a subdirectory in the root. Thus the compilation error above, as now I had two web.config files.
The solution is to move the backup out of the project root.