Using proper keyword density is a process that includes the strategic repetition of select, target keywords and minimization of nontarget keywords throughout your content. In this way you tell search engines that your Web site is relevant to search queries that you want to rank for. For example, if a specific word is used 5 times on a page containing 100 words, the keyword density is 5%.
The optimum value for keyword density is 3-5%. In the case of keyword phrases, you should calculate the total density of each of the individual keywords comprising the phrases to make sure it is within the specified limits.There are powerful keyword density tools like one located at the www.Webuildpages.com that helps you conduct keyword density analysis of your Web site. Ideally, you should optimize your Web site for at least 20-30 keywords. Each specific page in the Web site should be individually optimized for 1-2 keywords. The number of keywords varies with the type of Web site and the number of pages on the site.
In the past, keyword density was much more important aspect of the SEO process that it is today. The idea of using latent semantic content is replacing the idea of applying basic keyword density principles. Search engines rank Web sites not on the density of its target words but on topical relevance of semantically linked words. Covering as many semantically linked terms as possible within your content helps to get high relevancy of your Web site. Google Keyword suggestion tool as well as many other keyword research tools gives you an idea of what the search engine consider being semantically relevant words.