Say you are in a strange city and need a hotel for the night. You pull 
out your phone, search for hotels on Google and see a nearby one listed 
at the top of the rankings, with a little phone icon that says, "Call." 
You tap it, reach the hotel and ask for a room.And just like that, 
Google made money. That icon was a so-called click-to-call ad, and the 
hotel paid Google for it when you called.
As more of us have 
access to the Internet and apps through our cellphones and tablets, 
advertisers are looking for new ways to reach us there.
Some 
mobile ads remain just miniature versions of ads on Web sites, an echo 
of the early days of the Internet, when advertisers essentially slapped 
print ads online. But increasingly, advertisers are tailoring ads to 
phones by taking advantage of elements like their ability to track 
location, make a call, show maps with directions and add calendar 
alerts.
The stakes are significant for an industry that is still 
finding its way in the mobile world. Advertisers will spend a relatively
 small amount of money on ads on phones and tablets this year $2.6 
billion, according to eMarketer, less than 2 percent of the amount they 
will spend over all. Yet that is more than triple what they spent in 
2010.
"An ever-growing percentage of our ad buy is mobile because 
that's where the consumer is," said Chris McCann, president of 
1-800-Flowers.com, which has run mobile ads urging people to call or 
walk into a nearby store. "It's the future for us."
Coming up with
 ads that exploit the smaller mobile screen requires inventiveness from 
many parties - advertisers; digital publishers like Google, Apple and 
Facebook that sell ad space; and mobile ad networks like Millennial 
Media.
"What we're trying to do is think about the on-the-go 
user," said Jason Spero, leader of global mobile sales and strategy at 
Google, which dominates advertising online and is far and away the 
leader in mobile advertising. "What does that user want when she's 
sitting in a cafe or walking down the street?"
A big challenge for
 the tech companies is that advertisers pay less for mobile ads than for
 those online, largely because consumers are less likely to make a 
purchase on their phones. Though people click on mobile ads more than on
 desktop ads, advertisers wonder whether that is because of what they 
call the "fat finger effect" accidental clicks on tiny touch screens.
And
 while users' actions can be tracked across Web sites online, it is hard
 to know whether someone sees a cellphone ad for an offline business and
 then walks in so it is difficult for advertisers to judge how 
effectively they are spending their money.
As Google sells more 
mobile ads, the average amount it earns from each ad has dived. 
Facebook's value on Wall Street was halved on fears that it was not 
making enough money on its mobile users. Apple's mobile ad network, iAd,
 has been slow to gain traction.
Despite the problems, though, 
there is evidence that mobile advertising is becoming a meaningful 
business, and in some cases a bigger business than online advertising.
Facebook
 executives said last week that in the third quarter, the company earned
 $150 million from mobile ads, 14 percent of its total revenue. Pandora 
reported that in the second quarter that ended in July 58 percent of its
 revenue, or $59 million, came from mobile ads. Twitter executives have 
said that on certain days, the social network earns a majority of its 
daily revenue from mobile ads.
Mobile ad networks, which show ads 
across mobile apps and Web sites, have created new and thriving 
businesses. The biggest are Millennial Media, Google's AdMob and Apple's
 iAd.
Google earns 56 percent of all mobile ad dollars and 96 
percent of mobile search ad dollars, according to eMarketer. The company
 said it is on track to earn $8 billion in the coming year from mobile 
sales, which includes ads as well as apps, music and movies it sells in 
its Google Play store. But the vast majority of that money comes from 
ads, it said.
"Whoever does mobile best, they're going to be the 
next Google, so people are asking, 'Is Google going to be the next 
Google?' " said Chris Winfield, co-founder of BlueGlass Interactive, a 
digital advertising agency. "It still is Google's to lose."
Google
 and others have had success in taking advantage of the fact that mobile
 phones know a lot more about people than desktop computers do - most 
important, their location. And with a phone in hand, a customer is 
probably more likely to be ready to buy something.
People 
searching on a computer for jeans, for instance, most likely want to 
research styles and colors, while people doing the same search on a 
phone want the nearest place to buy a pair, said Mr. Spero at Google.
In
 addition, Google has benefited from the fact that one main way people 
use Google on phones is to search for nearby businesses, a prime source 
of advertising. Thirty percent of restaurant searches and 25 percent of 
movie searches are done on mobile devices, according to Google.
One
 of Google's most successful mobile ad types is the click-to-call ad. 
After running these ads, Starwood Hotels' mobile bookings grew 20 
percent in a month.
Google also shows ads on the mobile version of
 YouTube, including video ads like movie trailers before YouTube videos.
 If someone watches the movie trailer, Google makes money.
The 
company has also hinted that it could show ads through other services 
like Google Now, which sends unprompted alerts to cellphones. It coaches
 advertisers on how to do things like build mobile Web pages.
Larry
 Page, Google's chief executive, told analysts this month that thinking 
about mobile ads versus desktop ads is the wrong approach.
"We want a seamless experience that goes across mobile, desktop and TV, and that's what we're building," he said.
Pandora,
 the Internet radio service, is second only to Google in mobile ad 
revenue, according to eMarketer, which predicts it will bring in $229 
million in mobile ad revenue this year from both audio and on-screen 
ads.
An audio ad, for example, told Pandora listeners to tap the 
screen for the location of the nearest Whole Foods and a sushi lunch 
special. StubHub, the online ticket marketer, recently ran an ad on 
Pandora's app. Those who clicked on it received reminders for coming 
concerts to their cellphone calendars.
Gaining traction in mobile 
advertising is particularly critical for Facebook; 60 percent of its 
users log in on phones. But making the transition to the small screen 
has been a challenge: most Facebook ads appeared on the right side of 
the Web page, so there was nowhere to show them on a mobile device.
That
 is one reason Facebook started running ads in the newsfeed, like 
sponsored stories, which are notices that a friend likes a certain 
brand. It is also starting a mobile ad network to show ads on other 
cellphone apps, based on things Facebook knows about a user, such as 
what they like and where they live.
Twitter has inserted ads 
labeled "promoted" in its newsfeed from the beginning. On advertisers' 
behalf, Twitter can show ads only to people using mobile devices, like 
ads to download a mobile app.
Samsung showed an ad just to people 
using its Galaxy Note device, directing them to search and download 
Android apps for the phone.
Next, these companies must figure out 
how to persuade advertisers to spend more than 2 percent of their 
budgets on mobile devices.
"It's reminiscent of the Web in 1996, 
'97," said Michael Moritz, an investor at Sequoia Capital who financed 
companies like Google and LinkedIn. "People weren't interested in ads, 
and prices were low. But advertisers don't have a choice. They've got to
 go where audiences are."
© 2012, The New York Times News Service