Form Authentication and folder level Authentication

Hi Every one i am using Asp.net web forms .

i need to authenticate a specific Folder only Authorized user can access this folder i do the following code but this is not work.

<?xml version="1.0"?><configuration><system.web><authorization><allow users="haiderali@yahoo.com"/><deny users="*"/></authorization><compilation debug="true" targetFramework="4.5"></compilation><httpRuntime targetFramework="4.0"/></system.web></configuration>

How can i do this any one Help me for this????????