If you set a web folder attribute to hidden, users will receive 404 - File Not Found.

To prove this:

1. Set the WWWroot (or your default) to hidden.

2. Use your browser to browse to the folder.

3. You should receive 404 - File Not Found.

4. Set the attribute back to non-hidden.

5. You shou now be able to browse.

NOTE: Microsoft has acknowledged that this is a problem with all versions of IIS, from IIS 2.0 onward.