You can allow directory browsing (this should be an option from your hosting
control panel) otherwise speak to your host.
As I understand it, normally if you browse an URL such as
www.yourname.com/subfolder/ the browser looks for the index.html page. If
it doesn't find this the usual result is the 404 Not Found error. However,
if you turn on Directory Browsing, it will list all the files in that folder
instead (but only where there is no index.html file).
For this function you don't need the users to use FTP, it is a standard
function, that you can turn off and on, through your hosting control panel.
Again, speak to your host about this if you're not sure.
