New online ad model pays out when an ad leads to a specific action instead of whenever an ad is clicked Google is expanding a test it began last year of PPA (pay-per-action) ads, an ad format that is similar to pay-per-click ads but that experts say is much less prone to click fraud.In the PPA model, advertisers pay whenever the click on the ad yields a specific result, such as when users purchase something or complete an online form.On Tuesday, Google opened up its PPA test to more advertisers and publishers and gave them more automated tools for things like designing campaigns and creating ads, said Rob Kniaz, product manager for Google’s advertising products. The PPA ads run only on the AdSense for Content network of partner sites for now and are only available to U.S. advertisers and publishers. Site publishers can select individual ads or a set of ads or opt to have ads run that are contextually related to their site’s content.Participation in the PPA test is by invitation only. Publishers and advertisers can request to be included by going to the program’s Web page.Unlike PPA ads, the PPC (pay-per-click) model calls for advertisers to pay whenever a user clicks on their ads. PPC ads are vulnerable to click fraud, which occurs when someone clicks on a PPC ad without any intent to do business with the advertiser. Reasons for engaging in click fraud include the desire of a site publisher to increase commission revenue or the attempt by an advertiser’s competitor to drive up its ad spending. Technology Industry