Mobile Web usage has exploded worldwide, bringing more opportunites for mobile marketers than ever before, according to AdMob's September 2008 Metrics Report.

The study found that the Apple iPhone is now the No. 4 handset worldwide -- after Motorola RAZR, Nokia N70 and Motorola KRZR.

"We compared the top 20 devices in our network and 16 of the current top 20 devices are new," said Nicole Leverich, director of corporate communications at AdMob, San Mateo, CA. "All of the new phones deliver a better Web experience and have bigger screens.

"The fact that more consumers have advanced devices in their hands changes the landscape for marketers," she said. "Marketers can make richer, more engaging ad campaigns and not just a couple words for a text advertisement."

The growth in the usage of the mobile Web is widely distributed with 34 countries sending more than 10 million ad requests to AdMob's network in September 2008, compared to only 16 countries in September 2007.

According to AdMob, there were 103 million ad requests from iPhones worldwide in September 2008.

Other new devices, such as the Samsung Instinct and Apple iPhone, deliver an improved mobile Web browsing experience including larger screen sizes, faster network connections, and other enhanced capabilities.

In Britain, the Nokia N95 gained share steadily throughout the year and is now the leading handset with 9.7 percent share of requests.

The SonyEricsson K800i and W810i, the number 1 and number 5 handsets respectively in September 2007, both remain in the Top 5 a year later.

Worldwide ad requests fell 0.8 percent month over month to 5.1 billion, while ads served increased 26 percent to 4.5 billion.

U.S. requests grew 8.8 percent to 2.0 billion in September 2008.

AdMob is a mobile advertising network, serving more than 4.5 billion mobile banner and text ads per month.

Incorporated in April 2006, AdMob allows advertisers to reach their customers on the mobile Web and enables publishers to increase the value of their mobile sites.

The iPhone is the No.4 handset," Ms. Leverich said. "It has grown so quickly because it provides such an engaging experience for consumers.

"Marketers should look at iPhone users as a different, more technologically advanced demographic and tailor campaigns accordingly," she said. "The iPhone offers different ways to engage consumers and marketers need to take advantage of its advanced capabilities."