So you’ve built your website, you know what keywords you want to target (i.e. what words your customers are searching for), and you’re ready to write your copy. You’ve been told that you should use your keywords frequently so that you appear in search results for those words. But what does "frequently" mean? In order to understand optimum keyword usage, we first need to have some way of measuring keyword frequency. In the Search Engine Optimization (SEO) world, frequency is actually referred to as keyword density. In simple words, keyword density is the ratio of the word that is being searched for against the total number of words appearing on a given web page. If your keyword occurs only 2-3 times in a page of 500 or more words, obviously it has a lower keyword density than a keyword that would occur 8-10 times in a page of similar length.

As far as search engines are concerned, if a particular keyword has a higher density on a particular web page, then the chances of that page obtaining a much better search engine ranking increases almost exponentially. Not all search engines compute or evaluate keyword density in the same way and most have their own proprietary algorithm for calculating the average density of a keyword. Each search engine, from industry dominant Google, to Yahoo, to MSN Search, to the various other search engines, has a different keyword calculation. Some search engines permit heavier keyword numbers and density on the page, while some like Google, have much stricter allowable density levels. The placement of keywords, in any number of locations on the page, has different results in the various search engines as well.

The placement of keywords, in any number of locations on the page, has different results in the various search engines as well. Hence, you should try to write sentences that use your important keywords and key phrases.  However,  you should try and keep keyword density around 1.5% - 2%. If you overstep this limit there is a real chance of your site being penalized by Google.