You will have to collect a large number of high quality links from other Web sites if you want to improve search engine ranking of your web site. And they are known as inbound links. At the same time you can improve the link popularity by getting links from other high ranking sites. Google, the popular search engine provides much link popularity of website. If your site is linked to other sites you can get listed in Google without submitting your site to Google. If you can find more sites which are high in ranking, you can increase the search engine ranking.