These search engines allow webmasters to purchase positions within the regular search results. Webmasters decide how much they are willing to pay, and are then ranked according to that amount. Webmasters must deposit funds to the search engine, and each time their particular link is clicked by a visitor, the appropriate amount is deducted from that webmaster's account.

Our general advice is to place low bids on a large number of search terms. Paying $2 per click may obtain a high-ranking position, and may attract a lot of traffic, but you may also end up spending more to get those visitors than you can earn from them.

AdWords - Run by Google. Results appear on sites which are running the Adsense CPC program.

Big What - Geographically targeted. Bids start at 1¢.

FindWhat - Bids start at 1¢. Minimum deposit is $25.

GoClick - Also pays $2.50 CPM for their pop-under ad program promoting them, along with a search box affiliate program.

GoTo - Bids can be as low as 5¢, and submitted URLs are manually reviewed for relevance to the search terms. There is a minimum spend of $25 per month.

Search 123 - Feeds results to the Search Referral pay-per-search affiliate program.