Google Inc. has entered the mobile banner advertisement market with the launch of AdWords for mobile.

The mobile banners will be just like PC image ads, only smaller to fit on mobile screens and running on the mobile content network. The banner ads will be keyword-targeted, priced on a cost-per-click basis and link to a mobile Web site.

"For advertisers, mobile image ads serve as a branding tool and have shown to have good click-through rates," said Alexandra Kenin, product marketing manager of mobile ads for Mountain View, CA-based Google, in a blog post. "Advertisers using mobile image ads will also benefit because we only show one image ad per mobile page.

"For publishers, mobile image ads provide added flexibility," Ms. Kenin said. "They can now choose to show text ads, image ads or a mix of both and Google will dynamically return the ad that we expect will perform best at the time the ad is shown."

The Google banner ads will be available in four pixel dimensions: 305x64, 215x34, 192x53 and 167x30.

Publishers who already use AdSense for mobile content just need to update their AdSense code to start displaying mobile ads on their site.

Mobile image ads provide a new way to interact with mobile content, with contextual targeting making such ads more relevant.

Mobile banners via AdWords for mobile is available in Australia, China, France, Germany, India, Ireland, Italy, Japan, the Netherlands, Russia, Spain, Britain and the United States.

Until this debut there were only a few companies providing mobile banner advertisement services to the advertisers. These companies include Yahoo, AOL's Third Screen Media and AdMob.

"User experience is the key," said Jason Spero, director of marketing for AdMob, San Mateo, CA. "It is important that we, as an industry, prioritize a relevant and valuable user experience. Brand ads have been a big success for advertisers, publishers and for users on AdMob partner sites. AdMob is careful to adhere to the MMA standards to ensure a good user experience.

"We have found that the standard banner sizes deliver a relevant, proportional and valuable experience," he said. "When appropriate, we work with our customers to apply frequency caps to ensure that users do not see the same ads too often.

"Users' engagement is reflected in strong click-through rates for brand ads, ranging from 1 percent to as high as 7 percent. It is also important to note that we have not seen a material decay in click-through rates over the last year."

"The mobile ads work very well," said Sergey Brin, cofounder of Google, in a statement.

"There's nothing to dissuade me it would be any worse than traditional desktop search," he added. "Google has been working over the Android platform too, and now it is the mobile banner advertisement. Google seems to be keen towards mobile applications and services market."