To supplement their business models, certain text-link advertising networks (like Google) have expanded their network distribution to include “contextual inventory”. Most vendors of “search engine traffic” have expanded the definition of Search Engine Marketing to include this contextual inventory. Contextual or content inventory is generated when listings are displayed on pages of Web sites (usually not search engines), where the written content on the page indicates to the ad-server that the page is a good match to specific keywords and phrases.