Your HTML files, and or the files you want to make accessible to the World Wide Web must be uploaded to your account. When you first FTP into your account, you'll be taken to your "Home" directory. Don't confuse this with your "web directory." The home directory is "not" accessible to the World Wide Web; it's a private directory where critical system files reside. DO NOT delete files that have been created by the system, otherwise, your web site may disappear into cyber oblivion!
The "public_html" and "www" directory are the two directories, where files you want to be accessed from the web must be placed. Open the folder "public_html", which is your "web-accessible directory."
The folder named "www" is actually a shortcut to public_html, (both of them take you to your web directory). Upload the files you want your visitors to access to these folders.