Facebook on Friday tightened privacy controls for a controversial news feed feature, as founder Mark Zuckerberg apologized to hundreds of thousands of angry users, saying the social-networking site "really messed this one up."

While apparently well intentioned, the feature launched this week sparked protests among Facebook users who objected to its automatic broadcasting of members' activities on the site to everyone in their social circles. Two online petitions gathered a total of more than 700,000 signatures from members demanding that Facebook pull the plug on the new feature. In addition, a one-day boycott of the site was called for Sept. 12, and members were organizing a Monday demonstration at the company's Palo Alto, Calif., headquarters.

Facebook initially underestimated the anger over the feature, saying early this week that it involved only a small percentage of its more than 9 million members. The company believed protesters didn't fully understand the use of their privacy settings. That opinion, however, changed as the anger grew.

"We really messed this one up," Zuckerberg said in a Facebook posting. In releasing news feeds, "we did a bad job of explaining what the new features were, and an even worse job of giving you control of them."

Zuckerberg acknowledged that "this was a big mistake on our part, and I'm sorry for it."

To make amends, the company changed the privacy controls in the new feature by giving members the option to remove activities they did not want broadcasted over the news feeds, which protesters said violated their privacy and made them feel like they were being stalked. Such activities included posts on a discussion board and whether a person had left a group or network, or was single or in a relationship.

Organizers of the largest petition drive, Students Against Facebook News Feed, were cautiously supportive of the changes. The group said its initial impression was that Facebook had implemented most of the privacy changes petitioners demanded.

"Time will indeed tell if the new privacy options are satisfactory to the demands of this group," organizers said in a Facebook posting. "If the new privacy options do not indeed go all the way, do what you did before: complain."

Organizers, who gathered more than 600,000 signatures, according Reuters news agency, said they would decide in the next few days whether to disband.

The size of the protest drew the attention of major media outlets, and reflected the impact the Internet can have on a company that runs afoul of customers. The Facebook troubles also comes at a time when it and other social networks are looking to use their millions of members as a draw for advertising dollars.

Last month, Facebook said it would allow Microsoft to sell and display banner ads and sponsored links. The exclusive deal followed by about two weeks Google's agreement to pay News Corp. $900 million over three years to provide search and distribute advertising on MySpace.

Facebook in May was the third largest social network on the Web, followed by No. 1 MySpace and Classmates.com, according to ComScore Networks.