Yahoo! on Thursday announced that it bought a smartphone application maker whose backers included singer Justin Bieber, in its first acquisition orchestrated by new chief Marissa Mayer. The purchase of New York City-based Stamped was part of a focus on tailoring products, content and services to smartphones, tablet computers and other gadgets central to Internet Age lifestyles, according to Yahoo! senior vice president of emerging products and technology Stamped. \"Mobile is at the center of everything we do, every day, and at Yahoo!, it\'s become one of our most important priorities,\" Cahan said in a blog post. \"We\'ve acquired a very talented team based in New York City to help us create a new center of mobile product development for Yahoo!.\" Mayer marked the acquisition by posting at Instagram a picture of her at the Stamped headquarters with the startup\'s founding trio: former Google employees Robby Stein and Bart Stein, and Kevin Palms. Mayer left Google in July to take over as chief of Yahoo!, which has been struggling to re-invent itself after being eclipsed by Google in the online search market. Mayer joined Google in 1999 as its 20th employee \"and led efforts for many of Google\'s most recognizable products, including the development of its flagship search product and iconic homepage for over 10 years.\" \"As a team of mostly former Googlers, we\'ve all worked with and are big fans of Marissa,\" the founders said in a message posted at the Stamped website. \"So when an opportunity arose to become a part of the team at Yahoo!, we jumped.\" Stamped was founded about 18 months ago and in November released its first smartphone application that people can use to use \"stamps\" to show friends which films, shows, restaurants or other things they enjoyed. Financial terms of the deal were not disclosed.