Search engines are web sites that allow you to search the internet for content
Search engines are tools that allow web users to search for content on a particular web site or on the internet as a whole. Popular search engines include Google, Microsoft Bing, and AOL Search.
Many of your web site visitors will find your web site through the major internet search engines. Though most web sites only see 10-15% of their web site visitors coming to the web site from search engines, the search engines are an important source of new visitors and a very inexpensive way to get these new customers. Insuring that your web site is properly indexed by the search engines improves your chances of coming up in the search results when people are looking for your products and services.
To get your site listed in search engines, it is important that you include valid, accessible, relevant content; and that this content is marked up using valid and semantically correct markup.