Crawler Based Search Engines

Crawler based search engines Their listings automatically. Computer programs ‘spiders’ build them not by human selection. They are not organized by subject categories; a computer algorithm ranks all pages. Such kinds of search engines are huge and often retrieve a lot of information -- for complex searches it allows to search within the results of a previous search and enables you to refine search results. These types of search engines contain full text of the web pages they link to. So one can find pages by matching words in the pages one wants.