Set a Default Document
A default document is an HTML document that you specify as a property on a folder. A default document is used when a user requests a folder from the HTTP virtual server without specifying the name of a file within that folder. If you specify a default document, the HTTP virtual server displays that page to the user. If you do not specify a default document, a list of the folder's contents is displayed for the user to choose from.
To set the default document for a folder, send the PROPPATCH command as an HTTP request to the server. Set the value of the DAV:defaultdocument property to a string indicating either the absolute (http://server/virtualdir/folder/file) or relative (./folder/file) paths to the file. The request is sent using Microsoft Visual Basic script and the XMLHTTPRequest object available with Microsoft XML.
Note You can set a default document in IIS; however, Exchange does not use this information when processing requests against HTTP servers and folders created and managed in Exchange.
To set a default document: