• by Wendy Davis  @wendyndavis, November 8, 2006

Yahoo this week will roll out a beta test of banner ads on its mobile Web service. The launch advertiser, Pepsi, will use the service to market its Diet Pepsi soft drink.

Yahoo's move into mobile image ads comes about four weeks after the company introduced search ads on its mobile service. Rival Google in September launched a U.S. test of a service that allows paid search marketers to distribute pay-per-click and pay-per-call text ads to mobile phones.

The mobile ad market remains small for now--only $1.4 billion this year--but is expected to reach $2.9 billion by 2011, according to JupiterResearch. Most of the current mobile marketing efforts are centered on text-based ads, with image units remaining rare.

Currently, around 23.3 million mobile subscribers--or 12%--access the Web through mobile browsers, according to media measurement firm M:Metrics, which bases its figures on a monthly survey of 36,000 mobile phone users. Around 3.66 million mobile subscribers use Yahoo for mobile news, making it the second most popular mobile news service; CNN was no. 1, with 3.73 million subscribers, according to M:Metrics. Around 4.3 million mobile subscribers use Yahoo for search, while 5.3 million use Google's mobile search service, according to M:Metrics.