Pay per click (PPC) advertising was pioneered in 1997 by GoTo.com, which was later renamed Overture Services. Forrester Research recently forecast the pay per click advertising spend to reach $11.6 billon in 2010 becoming the dominant form of advertising on the Internet. Today the market is dominated by Google and Yahoo!, who bought out Overture in 2003. Ask Jeeves recently launched their own proprietary system and MSN will be entering the market in late 2005-early 2006. There are also a number of second tier players, including FindWhat and LookSmart that have been competing in the market for a number of years.

Pay per click advertising allows a company to bid on a keyword in a live auction marketplace. These keywords along with ad copy appear on the results page that a search engine returns for a user query. PPC ads are usually displayed at the top and bottom of each search return page and along the right hand side surrounding the natural / organic search returns. PPC ads can also be displayed on web pages that incorporate contextual marketing links, such as Google