Surfing the Web, as the term implies, is all about forward motion. And like the aquatic version, Web surfing against the tide poses quite a challenge. That's because the Web hyperlink is a one-way affair: it's easy to follow links from page D to pages E, F, or G, but the Web's architecture offers no simple way to see which pages-call them A, B, and C-link to D.  Programmers have tinkered with solutions to this problem since the early days of the Web. But interest in solving it has picked up recently with the spread of weblogs, most of which are personal sites full of links and commentary. In the last two to three years, hundreds of thousands of netizens have created weblogs to chronicle their daily lives, discuss the latest news, or share  expertise in their chosen fields.

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