ON THE INTERNET, THERE ARE TWO MAJOR CATEGORIES OF WEB RESEARCH TOOLS: RATERS AND ROBOTS. ON YAHOO, THE MOST WELL-KNOWN OF THE HIERARCHICAL INDEXES, SEARCHERS LOOK FOR SITES BY "DRILLING DOWN" - BY FIRST SELECTING A BROAD CATEGORY, VIEWING THE NARROWER SUBCATEGORIES, THEN CHOOSING UNTIL THE DESIRED SITES ARE LOCATED.
ANOTHER, NEWER SITE THAT WORKS THE SAME WAY IS CALLED LOOKSMART (HTTP://WWW.LOOKSMART.COM).