Google Page Rank
Google PageRank (PR) is Google’s method of calculating a web page’s relevance and importance through the quality of sites linking to it.
Google Link Popularity
Google, a popular search engine, is a tool for finding resources on the World Wide Web. Google scans web pages to find instances of the keywords you have entered in the search box.
Yahoo Link Popularity
The world’s leading search engine and directory before Google exploded. Still a strong second in the rankings and worthy of a visit.
BING Link Popularity
MSN Search was a search engine by Microsoft that comprised a search engine, index, and web crawler.