Crawler based search results are regulated by Organic SEO , Under this seo your website crawled by robots and spider and follow a linking based database of web pages of a website and after examining the nature of the website it allocates to their database .
Different crawler based Search Engines works on different algorithm thus ranking method of these search engines varies from each other , if you visit any SEO Forum you'll find a common question asked frequently that "
QUESTION - "WHY MY WEBSITE IS NOT RANKING ON FIRST PAGE OF GOOGLE WHEREAS IT'S RANKING ON YAHOO FOR THE SAME KEYWORD" ?
ANS - " ITS ONLY BECUASE ALGORITHEM OR THE METHOD OF RANKING GOOGLE USES IF FAR MOST DIFFERENT FROM GOOGLE FOR EXAMPLE GOOGLE USE"
