Expertise and authoritativeness of a site increases its quality. Be sure that content on your site is created or edited by people with expertise in the topic. For example, providing expert or experienced sources can help users understand articles’ expertise. Representing well-established consensus in pages on scientific topics is a good practice if such consensus exists.
As of 2009, there are only a few large markets where Google is not the leading search engine. In most cases, when Google is not leading in a given market, it is lagging behind a local player. The most notable example markets are China, Japan, South Korea, Russia and the Czech Republic where respectively Baidu, Yahoo! Japan, Naver, Yandex and Seznam are market leaders.

Optimization techniques are highly tuned to the dominant search engines in the target market. The search engines' market shares vary from market to market, as does competition. In 2003, Danny Sullivan stated that Google represented about 75% of all searches.[64] In markets outside the United States, Google's share is often larger, and Google remains the dominant search engine worldwide as of 2007.[65] As of 2006, Google had an 85–90% market share in Germany.[66] While there were hundreds of SEO firms in the US at that time, there were only about five in Germany.[66] As of June 2008, the market share of Google in the UK was close to 90% according to Hitwise.[67] That market share is achieved in a number of countries.