Keyword density is an indicator of the number of times the selected keyword appears in the web page. But mind you, keywords shouldn’t be over used, but should be just sufficient enough to appear at important places.
It is the search engines that finally bring your website to the notice of the prospective customers. Hence it is better to know how these search engines actually work and how they present information to the customer initiating a search.
If you’ve ever read an article about eBay, you will have seen the kinds of incomes people make – it isn’t unusual to hear of people making thousands of dollars per month on eBay.