Of course, it is not as if checkout pages are a delight to work with on desktops. But before mobile, when the shopping competition was buying online versus stores, the pain of dealing with a shoddy checkout page was dwarfed by the pain of getting in a car, going to the store, buying an item and driving back home. “In mobile, it’s mobile versus desktop, and if you want to drive transactions, you have to make it simpler than a desktop,” Mr. Epstein said. Few companies have more riding on mobile ads than Google, which became one of the world’s most valuable companies by building an advertising empire that began on desktop and laptop computers but is shifting rapidly to mobile devices. Google has reported that mobile searches have eclipsed desktop searches in 10 countries including the United States, and this year, for the first time, advertisers in the United States are expected to spend more on mobile search ads than desktop ads — $12.85 billion on mobile search versus $12.82 billion on desktop search, according to eMarketer. For the last several years, Google has seen a decline in an important measure of ad prices called cost per click, or the average price the company is paid each time a user clicks on an ad. “The experience you had on desktop was an e-commerce experience. You were researching, you were buying something or making a reservation, and that was a closed loop; we could track it,” said Jason Spero, Google’s vice president for performance media. Mobile phones blur the line between online and in-store shopping, because people often use them while shopping in stores, or to search for phone numbers to make purchases.
Google, Facebook, Twitter and Pinterest, are trying to bridge the gap between mobile browsing and desktop purchasing with a simple "buy" button, with technology companies acting as middlemen between mobile shoppers and retailers. The move is part of an effort by retailers such as Amazon (AMZN), Walmart (WMT) and Target (TGT, Fortune 500) to get more control over their customers' online shopping experience. Mobile phones are projected to account for about half the time Americans spend online this year, but only about one-fifth of retail e-commerce sales, according to eMarketer. Google recently rolled out ad formats such as hotel ads that allow people to book directly inside the ad, with a buy button coming later this year.