Before we can begin applying SEO techniques to a site we first need to understand how search engines determine what pages to list in their results. Search engines use automated programs (known as ‘bots’ or ‘spiders’) to ‘crawl’ the pages of the World Wide Web. Once a page has been crawled its contents are stored in the search engine’s database, a process known as ‘indexing’, and can then be found from searches. When a user performs a search the engine retrieves all the documents that match the search term from its database of indexed pages and orders them so that the pages deemed most relevant appear first. The key to SEO then, is to design a site so that it is deemed highly relevant for appropriate searches.