Frequency and proximity for search engines. In Internet there are many discussions about these expressions that not all webmasters understand. There are various professional software for these tests, but I can tell you from experience that not all look the same.
Keyword Density, Keyword Density refers to the percentage or ratio keywords that exist in a web page. It would be preferable that the percentage of keyword density to be about 3-9%. You can do a test for your pages here - www.live-keyword-analysis.com