Link popularity is a factor that many search engines use when ranking Web pages within their indexes. Simply put, most search engines give a ranking boost to sites that have incoming links from quality, related sites. This method of establishing importance, pioneered by the increasingly popular Google, is now used in some form by 19 of the top 20 search engines. While it is still possible to achieve high rankings for non-competitive terms without a great deal of link popularity, it is unlikely your site will rank well for very popular terms without it. So here's what to do about it.