NEW YORK - As a teenager, Tumblr chief executive officer David Karp would canvass the streets of the Upper West Side, offering to build websites for local businesses. After his freshman year of high school, the computer-savvy youth decided to drop out to devote more time to his passion for technology.

A few years later, Karp built Tumblr - the now-wildly popular blogging forum - from his tiny childhood bedroom, hunched over his laptop with bags of Tostitos. And on Saturday, the 26-year-old technology wunderkind returned home to inform his mother that Yahoo was buying Tumblr for $1.1 billion.

"There were a few tears and lots of hugs, and a lot of excitement," said his mother, Barbara Ackerman. "This is something that he built - it's his baby - and it's emotional."

Karp created one of the world's busiest websites. It boasts 75 million daily posts and a user base that's loyal, young, and hip. While Facebook has morphed into a mainstream social network where grandparents talk golf, Tumblr is that little corner of the Internet where the cool kids hang out.

With just six years of Tumblr's existence under his belt, Karp told the Associated Press that he still considers himself to be a green executive.

Today he's the "chief motivator, the guy jumping around every week to make sure the employees are excited about the product we are building and the direction we are headed in," Karp said.

"He doesn't have a pretentious or egocentric bone in his body," said Steve Nelson, the head of the Calhoun School, which Karp attended until the eighth grade. "He doesn't take himself too seriously."

Yahoo said Monday that Karp would remain in control of the service in an effort to retain the same "irreverence, wit, and commitment to empower creators."

Tumblr, which will remain based in New York, has a minuscule 175 employees compared with Yahoo's 11,300.

Yahoo CEO Marissa Mayer showered praise on her new employee, saying Karp possesses a rare combination of computer programming prowess and a sense of aesthetics.

"He will be one of the legends of his generation in terms of an entrepreneur who has really changed the way people express themselves," Mayer said.