Yahoo on Friday said it bought social web-browsing startup Rockmelt, extending a buying spree started shortly after Marissa Mayer became chief last year.

Yahoo did not disclose the financial terms of the deal, but technology news website AllThingsD valued the purchase at between $60 million and $70 million.

"The team has built a simple and beautiful technology that combines social, personalization and discovery to help you not only find what you're looking for, but also stumble across some cool stuff along the way," Yahoo senior vice president of mobile Adam Cahan said in a blog post.

Rockmelt launched in 2010 with Internet browsing software imbued with social features, such as sharing at Facebook or Twitter.

Buying Rockmelt was seen as a talent acquisition, with Yahoo weaving the startup's technology into its own products.

"The parallels between Yahoo and Rockmelt are obvious," Cahan said in the blog post.

"We can't wait to integrate the Rockmelt technology into our platform."

The Rockmelt buy comes just days after Yahoo snapped up a company specializing in software applications that help small businesses attract and service customers.

It also raises to 21 the total number of acquisitions made by Yahoo since Mayer took the helm a year ago with a mission to revive the withering Internet pioneer.

Yahoo's growing list of acquisitions includes Qwiki, a New York operation behind an application that converts video and pictures on iPhones into sharable movie clips complete with music soundtracks.

Yahoo has also bought Xobni, a startup behind tools for better managing contact lists and email inboxes, and Bignoggins Productions, a one-person operation specializing in fantasy sports applications for iPhones.

Yahoo in June completed a billion-dollar deal taking over the popular blogging platform Tumblr, a move aimed at bringing more youthful users into the company's orbit.

Since former Google executive Mayer became chief at Yahoo, the company has snapped up an array of startups including GhostBird, Alike, Stamped, Snip.it, and a Summly application built by a British teen.

Mayer's plan for reviving Yahoo's fortunes includes making priorities of mobile devices, video, personalized digital content, and elevating the company's popularity outside the United States.