This is not a normal 'index.html' file error.
Normally, if you don't have an index file of some sort you would see the directory.
I'm not hip on how they're doing their sites here, but it looks like something's not quite wiggled just right. You might need to dig back into the docs to see if there's a button that didn't get pushed or a file that needs a new name.
Good luck to you!
-Itico