HARTFORD, Conn. — Facebook, the world's second-largest social networking Web site, will add more than 40 new safeguards to protect young users from sexual predators and cyberbullies, attorneys general from several states said Thursday.

The changes include banning convicted sex offenders from the site, limiting older users' ability to search online for subscribers under 18 and building a task force seeking ways to better verify users' ages and identities.

"The agreement marks another watershed step toward social networking safety, protecting kids from online predators and inappropriate content," said Connecticut Attorney General Richard Blumenthal, who announced the agreement Thursday with his counterparts in several other states.

Officials from Washington, D.C., and 49 states have signed on.

"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."

Texas has not endorsed this agreement or a similar one reached in January among the other states, the District of Columbia and MySpace. Texas officials have said they want quicker action on verifying users' ages and identities than the pacts guarantee.

The attorneys general have been negotiating for months with Facebook and MySpace, the world's largest online social network with 200 million users around the world, for tighter controls.

"Social networks that encourage kids to come to their sites have a responsibility to keep those kids safe," North Carolina Attorney General Roy Cooper said. "We've now gotten the two largest social networking sites to agree to take significant steps to protect children from predators and pornography."

Facebook has more than 70 million active users worldwide. Messages seeking comment were left Thursday at its headquarters in Palo Alto, Calif.

MySpace, Facebook and other online networks have created a new venue for sexual predators, who often lie about their age to lure young victims to chat, share images and sometimes meet in person. It also has spawned cyberbullies, who have sent threatening and anonymous messages to other users, sometimes classmates and others they know.

Among other changes, Facebook has agreed to:

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

• Keep tobacco and alcohol ads from users too young to purchase those products.

• Remove groups whose comments or images suggest they involve incest, pedophilia, bullying or other inappropriate content.

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

• Review users' profiles when they ask to change their age, ensuring the update is legitimate and not intended to let adults masquerade as children.

The protections included in the MySpace and Facebook pacts could be expanded to smaller services such as Friendster and Bebo, Blumenthal said.

"We're entering a new era in social networking safety," Blumenthal said. "This agreement is open-ended in envisioning advances in technology that will permit even stronger steps in the future toward protecting kids' safety."