OK, but I think that answers that question - .org and .net are being redirected to
www.texasnissans.com/tx/forums, but
www.texasnissans.com is not so it just shows what you have in your root directory.
My guess would be that there used to be a file called index.htm in the root directory (if there isn't one, it will display the list of files like you see), and that it was just a static html page with that image and the "Enjoy the ride" message.