You will be able to Modify or Disable default documents through the IIS 7 Manager.

Log into your site using IIS 7 Manager.  Navigate to "HTTP Features/Default Document" to modify or disable the default document for your website.

The default document is a file that will be displayed without specifically calling the file in the URL. For example, if index.asp is set as a default document, and you upload index.asp to the /files directory, the URL http://HostingAccountDomain.com/files/ will display the index.asp page.

By default, a list of index pages with different extensions are preset as default documents for your account.

If you choose to disable 'Default Documents' for your site, the browser will return a "403—Forbidden" error if the name of the file is not specified.  As an example you use http://www.HostingAccountDomain.com and default documents is disabled, the browser will return an error.  

Note:  If Directory Browsing is enabled, the directory listing (all files in the directory) will be displayed.