Sidebar: The deep, dark, invisible shadow

This Quickstudy uses the term deep Web. Similar-sounding terms that sometimes appear are dark Web or dark Internet, but they actually refer to stand-alone machines or network segments that are not connected to the Internet and thus are inaccessible online by people or search engines. Yet another, less common, term is shadow Web, which more often refers to a particular Web server or to a specific Web community than to the deeper reaches of the World Wide Web. Finally, there's invisible Web, which is probably the oldest and most popular term (having been coined by Jill Ellsworth in 1994). We avoid it here because it is a less accurate descriptor; such content is indeed visible to the average user, but normal search engines can't index or query it. With appropriate technology and more sophisticated search sources, the deep Web is almost totally "visible."