--> It is a very important factor to increase your webpage ranking. Keyword density is the percentage of a particular phrase or keyword included on a web page compared to the total number of words on that particular page.
Keyword density is an important factor for a high quality content. You should maintain your keyword density between 2.5 to 3 per cent for best results in search engines.
Keyword density is the percentage of words on the web page which match a specified pair of keywords. In the context of seo keyword density can be utilized as a consider determining whether a web site is relevant into a specified keyword or keyword phrase. Due to the simplicity of managing keyword occurrence, search engines commonly implement other measures of relevancy in order to avoid unscrupulous webmasters coming from creating search junk e-mail through practices for instance keyword stuffing.
I'm sure that's how websites like IGN got sooo successful. They focused more on keyword density than creating content for real humans who actually want to read the content.