An error to use a section registered as allowDefinition='MachineToApplication' beyond application level

Dear Sir

I have created one web page that contains AJAX controls.
application Contains one master page and two more web pages.
It contains two web.config file.
In one PC application gives O/p but another PC it gives follwing error.
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.

Please give me reply as soon as possible

Thanks in advance