N.J. It was published in Thursday's issue of the journal Nature . Lawrence and Giles estimated that as of February, the searchable Web consisted of 800 million pages containing more than 6 trillion characters. Their December 1997 survey put the number of pages at about 320 million. By comparison, the 532 miles of shelves in the Library of Congress contain an estimated 20 trillion characters. These tend to be good for finding and ranking information which is well known and has been around for a while,'' he said.
Search engines use computers called ''spiders'' that continuously surf the Web.
They save each page they visit, then follow the links on the page to find other pages. When a user types in a word, the engine looks in its index to see which pages contain it. A page that's not listed in the index will not be found. The spiders are more likely to find pages that have more links going to them from other pages. Lawrence said that might make it hard for new sites to make it into search engine listings.