What is Link Popularity?

Link popularity is the total number of web sites that link to your site.

Why is it important?

Because good link popularity can radically increase traffic to your web site. Strategically placed links are an excellent source of steady, targeted traffic.
The major search engines factor Link Popularity into their relevancy algorithms. By increasing the number of quality, relevant sites which link to your site can in fact improve your search engine rankings.

Quality vs. Quantity

Quality is most important. It doesn’t do your website any good to have a bunch of unrelevant sites linking to it. There are plenty of "linking farms" out there that promise you 1000’s of links, but if they are not relevant you are risking your websites placement in the search engines.

Factors affecting link quality
- Relevance
- Popularity
- Anchor Text
- Age

What is Page rank? How does it factor into Link Popularity?

PageRank is a numeric value that represents how important a page is on the web. Google figures that when one page links to another page, it is effectively casting a vote for the other page. The more votes that are cast for a page, the more important the page must be. Also, the importance of the page that is casting the vote determines how important the vote itself is. Google calculates a page's importance from the votes cast for it. How important each vote is is taken into account when a page's PageRank is calculated.
PageRank is Google's way of deciding a page's importance. It matters because it is one of the factors that determines a page's ranking in the search results.

Page rank effects link popularity because if a highly ranked, relevant site links to you that is better than a lower page ranked site linking to you. Age, popularity and relevance!