It is an error to use a section registered as allowDefinition='MachineToApplication' beyond application level. This error can be caused by a virtual

Solution:

1.Not configured your asp.net application in IIS. If you have not Configure your application to run on IIS First Configure your Site to Run on IIS.For that Create Virtual Directory From IIS and Give Permission to Application (Read,Write) .

2.Other solution is they might be too many Web.Config Exists on your Site.Just Remove this Subfolder web.config from Subfolder.