Yahoo! Inc. (NASDAQ:YHOO) paid more than $50 million for Rockmelt Inc., a person with knowledge of the matter said, as Chief Executive Officer Marissa Mayer seeks to revive the Web portal by adding staff and technology from startups.

The deal values Rockmelt, a developer of Web-browsing software, at as much as $70 million, said the person, who asked not to be named because terms of the acquisition weren’t announced. Rockmelt said it’s shutting down its website and applications on Aug. 31.

Mayer has spent more than $1.2 billion to buy at least 20 startups in a shopping spree focused on bringing top engineering talent back to Yahoo. Rockmelt’s team and underlying technology will help Yahoo build tools for browsing content on the Internet and mobile devices, the startup said on its blog.

“Yahoo and Rockmelt share a common goal: To help people discover the best content from around the Web,” Rockmelt said in the posting. “We plan to put everything we’ve learned to work at Yahoo.”

Lauren Armstrong, a spokeswoman for Yahoo, declined to comment on terms of the deal. The technology blog AllThingsD earlier reported that Yahoo paid $60 million to $70 million for Rockmelt.

Founded in 2008, Rockmelt had raised $40 million from top venture capitalists including Marc Andreessen and Vinod Khosla, who both served on its board. The startup began as a Web browser that incorporated social-networking features from Facebook Inc., and more recently developed mobile apps for reading popular articles and sites on the go.

Recent Buys

Yahoo earlier this week disclosed that it has acquired Palaran Inc., the operator of e-commerce service Lexity. That followed recent deals for contact-management company Xobni Corp. and mobile-video tool Qwiki Inc.

Mayer, who joined Yahoo a year ago, has made improvements to messaging products in her bid to win users and advertisers from Facebook and Google Inc.

Yahoo fell 1.1 percent to $27.65 at the close in New York, leaving the shares up 39 percent this year, compared with a 20 percent gain for the Standard & Poor’s 500 Index.