Google Inc. (Nasdaq: GOOG), owner of the world’s biggest search engine, agreed to buy Meebo Inc., a startup that helps online publishers make their websites more social.

Meebo, founded in 2005, announced the agreement today on its blog. While terms weren’t disclosed, the price was close to $100 million, according to a person with knowledge of the deal, who declined to be named because it hasn’t been made public.

Google is bolstering social features for its Google+ network as it tries to lure users from Facebook Inc. (Nasdaq: FB).

Meebo, based in Mountain View, California, provides software that lets Internet sites share pages on Twitter Inc. and Facebook and allows advertisers to promote products in interactive ways, such as through a bar that pops up at the bottom of a Web page. The company says it reaches half of the U.S. Internet population through partnerships with media sites.

“With the Meebo team’s expertise in social publisher tools, we believe they will be a great fit with the Google+ team,” Google, also based in Mountain View, said today in a statement.

The companies’ discussions and the price of the deal were reported last month by technology blog AllThingsD.