Next time you log onto MySpace or YouTube, take some time to reflect that social networks like these owe everything to the genius of Ted Nelson, who in the 1960s invented hypertext, the technology that allows you to navigate between documents on the web. Mike Holderness sat down with Nelson to explore a few of the networking websites that his ideas have enabled

What is the connection between hypertext and online social networking?

It's all built on a certain kind of hypertext. Whenever you post a comment on someone's web page or link it to yours, for example, you make a sort of hyperlink.

Why should we care about what kind of hypertext underpins it all?

Because this determines which ways of using social networking are easy, which are hard, and which are impossible.

Let's look at www.myspace.com/hdif, which is a page in the MySpace network run by ...