Keywords on site

Once you’ve selected a blog and decided what to write about, the real work begins, you need to start optimizing the site not only for the generic keywords of the site, but also for the keywords of each individual post.

as a general rule best practice means that keyword density for a site should be around 3% to 9%  so this should be reflected in every article/post, at the same time for each specific article, the ’sub-keywords) or keywords specific to that article also need to be between 3%-9% however in this case, it may be alot less relative to the generic and over all keyword density of the site.

The significance of this is again in helping to boost your position in Googles page ranking. by having the right  amount of keyword density Google determines that your site is accurate and worth ranking more highly due to relevancy to the subject being searched.

This element of Keyword/ SEO is termed as on page SEO.