Search engines give the most importance to the keywords that placed at the beginning of the article and HTML tags.The web sites that you are competing against for top placement of a particular word and the specific search engines ranking your pages will place a large influence on how the strategic placement of your keywords will affect the placement of your site in search results.
Keyword place in web content is also important.
Always put one keyword in first paragraph of content and do not exceed the limit of keyword density beyond 2%-3%