Its not so much the occurrence of a word, but the power of the word within the content. You could look at it as a percentage.
There are however a lot of factors to take into account. A word in a heading will carry more value, titles will carry a lot more value and text that stands out will also have more value when it comes to density.
Don't make the mistake of going all out go really boost your keyword density, this will only lead to an over optimisation penalty.
Carry out searches and see what sites rank well. Go over their source cone and note down occurrences of words and where they are placed.
Don't even consider keyword density. As previously mentioned, it is a sure fire way of triggering an OOP.
Write naturally, in an easier to read way for the target audience.
Add your target keywords in your headings and title tags, yes, as this adds to the "relevance" of the page.
There is no "right" number of times for a keyword to be used that will make your content more effective, so I wouldn't worry about keyword density at all. The key is to write content for your human reader FIRST and then naturally optimize the titles, headings, Meta descriptions and content to make it more "SEO friendly." But if you find yourself having to force a keyword into the content it means you shouldn't do it.
3 to 4 % keywords density is good for any webpage. I have checked website with 3 to 45 keywords density ranks well in search engine for targeted keywords. I think keywords placement in meta tags, h1, content and footer text is the perfect way.
Keyword density is when a 200-300 word article contains 2-3 % of keywords. This is the best density of keywords for better optimization of websites on search engines.
Keyword density means visibility of your keywords in your content. How much times your keyword has repeated. Your keyword density should be 3-5% for better optimization.
It is the percentage of times your keyword phrase appears on the page.
You can calculate it by using the formula
(Total Keywords / Total no. of words on the page) * 100
Make sure that your keyword is in the title tag, description tag and h1 tag at minimum. I will say that the percentage would be between 2 and 4%.
[edited by: tedster at 2:37 pm (utc) on Apr 27, 2013]
[edit reason] No signature links please [/edit]
Occurrence of a keyword on a webpage is known as Keyword Density. Their are many online tools that helps you to check the density and it lies between 3 to 4 %.