Firms of search engine optimization have formed early in United States. Now there are innumerable SEO companies and many companies doing search engine marketing through the SEO services. In the case of America, 'Google' is occupying American search engine marketplace with the share of search engines near 50 percent. And 'Google' is the organic search engine, so the results of organic search are established by ‘Googlebot’. Therefore, it is very important to optimize with the character of ‘Googlebot’.