The following factors play a part in the portion of the Google algorithm that determines page relevancy. Google looks at the following keyword factors and assigns a relevancy score for each page of your site. The factors are listed in approximate order of importance, however, like all factors in the Google algorithm, this is subject to change.
Google looks at individual words that make up phrases. Keyword proximity is a measure of word order and closeness. The closer all words in a keyword phrase are together, and in the correct order, the better.
Obviously, exact matches score the best. As an example, say someone does a search on “country house plans”. Google will assign a higher score if your page contains “country house plans” than if it contains “country and farm house plans”. For the latter, all three words are contained on the page, so the page would receive some score, but since this is an inexact match (there are words in between “country” and “house”), the page score would be lower than for the exact match of country house plans.
This measures where on the page keywords are located. Google looks for keywords in the page title, in headings, in body text, in links, in image ALT text and in drop-down boxes.
A measure of how early or high up on a page the keywords are found. Having keywords in the first heading and in the first paragraph (first 20 words or so) on a page are best.
Also known as keyword weight, the number of times a keyword is used on a page divided by the total number of words on the page. There is some confusion over keyword density. Part of this stems from the fact that different software programs look at different parts of the page and calculate this differently.
There doesn’t seem to be an ideal density value for Google. Just don’t spam. In other words, don’t fill your pages up needlessly with your keywords – not only will customers think your site is amateurish, but Google may penalize you.
Keyword density used to be more important in the past for search engines, and you may still find books that stress the importance of this factor. For Google, it is not important so don’t get hung up on it.
A measure of whether keywords are bolded or italicized on the page. The best place to do this is in the first paragraph of the page. This isn’t a real important factor, but every little bit helps