Although far smaller than rivals Google and Yahoo! search firm Quigo is winning important advertising business from its competition based on a non-threatening advertising strategy.

Quigo's AdSonar online advertising system works like Google's AdSense and Yahoo!'s Content Match, but scores highly in winning business away from search engine rivals, firms which are increasingly competing with would-be advertisers.

Recently ESPN.com defected from large ad network Yahoo! in favour of Quigo's contextual advertising system, which allows advertisers to target article keywords or specific ESPN channels. But other ESPN Yahoo! partnerships remain in place.

Internet market research expert Greg Sterling told CNN: "Quigo is benefiting from a perception of independence. There is general angst about the power that Google and Yahoo! have and Quigo is able to sell against that."

A further advantage of the Quigo system is that it allows sites to sell their own text adverts from an interface that they manage, as AdWeeks' Brian Morrissey pointed out to Search Engine Journal.

"By selling their own text ads, sites are able to keep all of the revenue and maintain relationships with advertisers. Typically, Google and Yahoo! give publishers about 80 per cent of revenue generated from clicks on their ads."