The "www" is actually the alias for the site's webserver. The machine's actual name might be almost anything -- I've known of them named Snoopy, Dopey, Sneezy, Uriel, and other names. You might very well run across a web address like "customwire.ap.org" with no "www" at all.

Usually, I just ignore it altogether. When the address actually has no "www" I make this clear to whoever I'm talking to.