Move over spam, there's a new ad scheme called Toptext that is delighting advertisers and drawing ire from users who view it as yet another obnoxious online advertising gimmick.

Popularised by a California firm called Ezula, Toptext technology highlights words on a web page which then link you to an advertiser. But for those who have unknowingly downloaded and installed Toptext, the technology is more a scourge than a revolution.

Toptext, which works with Microsoft's Internet Explorer browser, is typically bundled with free software programs and is currently being distributed with popular file sharing software such as iMesh and KaZaa.

But while advertisers are seeing results with Toptext, critics view the technology merely as the latest iteration of intrusive advertising, likening it to pop-up and pop-down ads.

Nonetheless, Ezula says its Toptext program has been downloaded more than a million times since the service's April launch. Currently Toptext works with 30 advertisers, and highlights 7,000 keywords.

"There is always someone who is going to complain," says Henit Vitos, Ezula's co-founder. Most objections, she says, come about because people didn't pay attention when installing the program with which Toptext was bundled. She points out that you can simply uninstall Toptext through Add/Remove programs feature in Windows.

Keywords appear on web pages with thick yellow lines below them and become hyperlinks that connect to advertisers. For example, when the phrase 'hip hop' appears on a website you can click on it and you're taken to an advertisement for BMG Music Services.

Toptext is what is called 'contextual advertising', the advertising industry's latest attempt to reach consumer eyeballs online by placing ads based on the context or subject of the text on a web page. The novel advertising system also underscores the increasing financial pressures on internet companies to develop stable revenue streams.

"What we're seeing is a lot of experimental advertising," says Stu Ginsburg, spokesperson for the Interactive Advertising Bureau, a US trade association that sets guidelines for online advertisers. "Online advertising is constantly evolving. It will always test the boundaries of what is annoying and what works."

Ezula technology is similar to SurfPlus and AdPointer. Each is a program you download, which creates hyperlinks within the text of a website linking to advertisers. In the case of Ezula, advertisers buy keywords or phrases. Advertisers pay between 30 cents and one dollar for each click that word or phrase receives. That may seem steep, but Ezula claims 25 percent of those that click on a link take some sort of action at the advertiser's website.

Ezula has set some online bulletin boards buzzing with comments from angry users who feel they were tricked into downloading the program.

Some within the advertising industry call Toptext 'guerrilla' advertising because it gives rival companies the ability to manipulate and advertise on a competitor's website.

At least one analyst suggests Ezula's Toptext advertisements may be short-lived.

"The issue is whether or not these ads are relevant to the consumer and are genuinely helpful," says Carl Lehmann, vice president of electronic business strategies at the Meta Group. "Are these ads better? In theory they make a lot of sense, but in practice they don't."

He says consumers have a low tolerance for annoying technology.

"If Ezula can't live up to its promise," Lehmann says, "consumers will delete Toptext and never think twice about it again."