Keyword Density & SEO
Keyword density (sometimes referred to as 'keyword frequency') is an important SEO factor for 'on page optimisation', perhaps the second most important 'on page optimisation' factor after the page title. You must assign a keyword to a page on your site and make sure the bots know that this page concerns this assigned 'keyword string' and will you please rank it...
When the page starts to rank, users will share it (if the content is good??), the page will receive more backlinks, more traffic and going forward the search position for that page will increase. So, how frequent should the page keyword be repeated, what percentage of the article?
Keyword Density SEO Best Practice
Relevancy of content has a lot to do with keyword density, and the keyword density of the page or blog post should be between 3 and 7% of the article.
It is thought that making the assigned keyword italic or bold tells the bots what you want them to rank the page for.
Keyword Density - What not to do
DO NOT go above 7% keyword density, if a term is mentioned once on a page, that page likely won't rank as high as one mentioning that term 10 times. That said, spamming the page with a hundred instances of a keyword will damage your ranking
DO NOT use "invisibly" text, that is using coloured text on a matching coloured background
From a technical point of view, be aware of the keyword density relative to the overall amount of code used to display the page. Search engines only look at the visible text for this, and only crawl so far into each page. So, if your page uses a lot of code before it ever gets to the article, your carefully crafted article might not even be seen by the search engine's spider.