In the span of a decade, the World Wide Web, in short WWW has grown from a small research project into a vast repository of information and a new medium of communication. Today, many organizations (Governmental, Non-Governmental), Institutions, Business organizations etc., use Web as their information media and Internet has become an indispensable part of day-to-day life. Unlike other great networks of the past century, - such as the electronic power grid, the telephone system, or the highway and rail system, - the Web does not have an engineered architecture. Rather, it is a virtual network of content and hyperlinks with over a billion interlinked “pages” created by the uncoordinated actions of tens of millions of individuals.

WWW can be viewed as a graph, in which each node represents the page and edges connecting the nodes are the hyperlinks. The topology of this graph determines Web’s connectivity and consequently how effectively can we locate information on it. But, its enormous size estimated at least 8x108 documents and rapidly growing poses a big challenge to search related pages for specific topic. Major search engine companies have often claimed that they can keep up with the size of the Web. But, due to its continuous changing of documents, links and rapidly growing nature make it impossible to catalogue all the vertices and edges. The estimated coverage of the web by some search engines is given in table below.