Spiders The search engine sends out a ‘spider’ or ‘robot’ that records all the text on your website. That text is then indexed in a database, categorized by keyword, and given a relevancy ranking. A higher relevancy ranking makes your pages appear higher when the search engine returns results to a visitor.
Main Engines – Google, Yahoo, MSN
Benefits – These are the Big Three and they cover 95% of all search engine traffic. Concentrate your efforts here and forget about the little guys.
Directories Directories have websites submitted to them for review. The best directories are reviewed by hand and disallow affiliate sites or sites with little or no content. Most directories get very little traffic but, since the included websites are reviewed for quality, the Big Three consider them a good source to find new websites. Getting listed in directories is the most common way to build link popularity.