it's an asp.net mvc app. installed under root dir. but still keep get 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: 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. Source Error: Line 56: ASP.NET to identify an incoming user. Line 57: --> Line 58: <authentication mode="Forms"> Line 59: <forms loginUrl="~/Member/LogOn" timeout="2880"/> Line 60: </authentication> How to fix it? it's automatically configged as app under root dir, right?