SAN FRANCISCO — 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 on our cellphones and tablets, advertisers are looking for new ways to reach us there. Some mobile ads remain just miniature versions of ads on websites, 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 such as their ability to track location, make a call, show maps with directions, and provide calendar alerts.
The stakes are significant for an industry 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 — about $2.6 billion, according to eMarketer, less than 2 percent of the amount they will spend overall. 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 a leader in mobile advertising. ‘‘What does that user want when she’s sitting in a cafe or walking down the street?’’
A challenge for 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 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 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 mobile advertising is becoming a meaningful business, and in some cases a bigger business than online advertising.
Google, the search giant, has had success in taking advantage of one aspect of mobile phones: those phones know a lot more about people than desktops do — most importantly, their location.
People searching 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 store to buy them, said Spero at Google.
Google has benefited from the fact that one main way people use Google on phones is to search for nearby businesses, a key source of advertising. Some 30 percent of restaurant searches and 25 percent of movie searches are done on mobile devices, according to Google.
One of Google’s most successful ad types is the click-to-call ad. After running these ads, Starwood Hotels’ mobile bookings grew 20 percent in a month.
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.