Keyword density means on Search Engine for higher Ranking

The keyword density tool is useful for helping webmasters and SEOs achieve their optimum keyword density for a set of key terms.

Keyword density is important because search engines use this information to categorize a site's theme, and to determine which terms the site is relevant to. The perfect keyword density will help achieve higher search engine positions. Keyword density needs to be balanced correctly (too low and you will not get the optimum benefit, too high and your page might get flagged for “keyword spamming”).

From : SEO chat room

http://www.seochat.com/