This book is all about the working of search engines and effective ways which can be implemented to gain good ranks .Web crawlers was our research topic during our Masters studies for which we thank alot to Mr T P Singh, Assistant Professor, Sharda University to help us through out our work.We also thank our mother and father for the same.Last but not the least we thank Almightly God whose blessings always helped us in carrying out our research work. A brief idea of working for optimization is also described which we had experimented for couple of websites.