In the "small world" theory of the Web, every Web page is thought to be separated from any other Web page by an average of about 19 clicks. In 1968, sociologist Stanley Milgram invented small-world theory for social networks by noting that every human was separated from any other human by only six degrees of separation. On the Web, the small world theory was supported by early research on a small sampling of Web sites.
What is the significance of the "bow-tie" form of the Web?
The researchers discovered that the Web was not like a spider web at all, but rather like a bow tie (see figure below). The bow-tie Web had a "strongly connected component" (SCC) composed of about 56 million Web pages. On the right side of the bow tie was a set of 44 million OUT pages that you could get to from the center, but could not return to the center from. Finally, there were 16 million pages totally disconnected from everything.