Search engine optimization (SEO) is the process of improving the volume and quality of traffic to a web site from search engines via natural (organic or algorithmic) search results. Usually, the earlier a site is presented in the search results, or the higher it ranks, the more searchers will visit that site. SEO can also target different kinds of search, including image search, local search, and industry-specific vertical search engines. As a marketing strategy for increasing a site's relevance, SEO considers how search algorithms work and what people search for. SEO efforts may involve a site's coding, presentation, and structure, as well as fixing problems that could prevent search engine indexing programs from fully spidering a site.