One of the major departures of the Yahoo! algorithm from that of Google is in the tolerance levels of keyword usage. Yahoo! simply permits more keyword placement on the page. At rates that would probably be targeted by Google as keyword stuffing, Yahoo! even rewards almost blatant over use of your main keywords and phrases.
The generally accepted level of keyword use permitted by Google is thought to be between 2% and 3% of overall word totals. Any more keyword usage than that amount could often trigger a keyword stuffing filter. There is some thought that Google may have even cut its tolerance for keyword use down to the area of between 1% and 2% of content copy. Yahoo! allows, and some say even rewards, far higher amounts of keywords on a page than does the Google algorithm.
One thing is almost certain. Yahoo! tolerates higher levels of keyword density. What that means for you is an opportunity for some real flexibility in your writing your on page copy. Keep in mind the Google approved level of keyword density and combine it with Yahoo!'s encouragement of heavier word placement. That is not necessarily a contradiction in terms either. There are techniques for perhaps enjoying the best of both search engine worlds in the area of keyword density.
One of the best methods for providing keyword density, without stuffing the copy with an oversupply of keywords, is through the use of synonyms. As you know, a synonym is a word that means the same as another. By means of synonyms you can take advantage of the chance to gain even more searchable keywords without getting into trouble with the Google algorithm. The Yahoo! algorithm should treat you well for your writing. The Yahoo! search algorithm is thought to be more language based than Google and therefore rewards variety in your copy.
Some SEO professionals believe that the Yahoo! algorithm is more sensitive to stemming than is the Google search engine. Stemming is the use of different forms of a word. That includes either the plural of a word, or one with a slight change of word form. If this is indeed the case, then your copy can be written in more natural form. Better written content not only helps with search engine rankings but serves to better inform and to convert your visitors into customers.
While search engine optimization gets the majority of the attention from SEO professionals, consideration should also be given to your site visitors. High search engine rankings mean little if your copy doesn't convert your visitor traffic to paying customers. For that reason, care should be taken in the creation of your on page written copy.
As a content provider, you can write for both search engines and real world visitors. Use natural language, and your site will work well both ways. Just because the Yahoo! algorithm supports what Google would consider keyword stuffing is no reason to do it. Think of the purpose of your site first and foremost in every aspect of your copy writing and your optimization efforts. The focus should be on profitability and the bottom line.
Yahoo Optimization 
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