It is known that Google takes into account over 100 different variables when creating an algorithm for ranking. Whilst we may wonder how to master each and every one of these facets, we can be sure that keyword density is one of the most important variables and should be the first to consider to optimize our site. Keywords are the words and phrases that are entered into search engines so that they can produce the results that the surfer is looking for. It is the work of the search engine to find relevant information based upon these keywords. So if we enter the keyword 'bicycle' into the search engine, we do not want to look at an article that has this word mentioned only once throughout. In this case, it is unlikely that the result would be relevant at all. This is reason for the importance of keyword density as a variable. Obviously, if the article mentions the keyword 'bicycle' ten times, then it is a much better match for the keyword search since it is likely to contain the information that the searcher seeks.

Keyword density refers to the number of times a given keyword is mentioned in an article. It is found by dividing the number of occurrences of the keyword by the total number of words in the article. So, if you have an article with 10 keyword occurrences out of 200 words, the keyword density is 2%. Although it varies by search engine, a good rule is to maintain keyword density between 3 and 5 percent. Also, articles with the keyword in the title are generally considered more relevant than those without. It is also important to remember that search engines will penalize you for blatant plastering of keywords, so do not exceed 5%!

Primary keywords are the precise phrases keyed into the search engine. Tier one keywords are those that are the same as the primary keyword, but with a slight change in grammar. "Bicycle parts" would be a tier one keyword for "bicycle part". Ideally, they should be used only once in the first or second paragraph. Tier two keywords are words that one would relate to the primary keyword. For "bicycle part", tier two keywords would be things like: seat, handlebars, spokes, wheels, or any other word that may be in an article related to bicycles. These words should simply appear naturally throughout the article without any emphasis on keyword density. The last component is keyword variations. For "bicycle part", they would be: bicycles, part, parts, and bicycles. These need to be used throughout but should not exceed 4% in total density.