The agreement with attorneys general in 49 states and the District of Columbia would ban convicted sex offenders from the site and limit older users' ability to search for underage subscribers.

"Pennsylvania continues to be one of the leading states concerning Internet safety for children," said Pennsylvania Attorney General Tom Corbett, who announced the agreement with his counterparts. ". . . This agreement is another step we've taken to protect the innocence of children."

Facebook has more than 70 million users worldwide.

The agreement is similar to one reached in January with MySpace, the world's largest social networking site, with 200 million users worldwide.

Facebook said in a statement that the company is committed to keeping children safe on the Internet.

"Building a safe and trusted online experience has been part of Facebook from its outset," said Chris Kelly, Facebook's chief privacy officer. "The attorneys general have shown great leadership in helping to address the critical issue of Internet safety, and we commend them for continuing to set high standards for all players in the online arena."

Among the provisions is one aimed at preventing older users trying to masquerade as youngsters. The agreement stipulates that when a user tries to change their age, their profile will be reviewed by a customer-service agent.

Some law enforcement officials question the agreement's ability to screen out predators who lie about their age.

The Texas attorney general opted out of both agreements over concerns about the inability to verify the ages of the sites' users.

"This agreement is not an all-clear sign that it is safe for children to go onto MySpace," Abbott told The Inquirer in February. Any predator "can go on there right now and establish a profile as a 15-year-old. That poses a great danger."

Eric Shirk, a spokesman for the Pennsylvania Attorney General's Office, acknowledged that the agreement wasn't perfect but called it a "preventative step."

The agency has arrested 143 individuals since the creation of its Child Predator Unit in 2005, none of them using a Facebook account, said Shirk.

A spokesman for the New Jersey Attorney General's Office said that it has not had any Facebook-related arrests.

Last year, the special predator unit of the Pennsylvania Attorney General's Office made 54 arrests. Of those arrested, 31 had MySpace accounts.

Agents in New Jersey said they worked with MySpace and Facebook to remove hundreds of sex offenders who had profiles with the sites.

Under the agreement Facebook will join the industry-wide Internet Safety Technical Task Force, created after the agreement with MySpace, to develop age- and identity-verification tools.

Among other changes, Facebook has agreed to:

- Ensure that companies offering services on its site comply with its safety and privacy guidelines.

- Remove groups whose comments or images suggest incest, pedophilia, bullying, or other inappropriate content.

- Send warning messages when a child is in danger of giving personal information to an adult.