Google, Yahoo and Microsoft, along with several human-rights groups, have announced a common code of conduct relating to freedom of expression and the protection of privacy online.

Through a new organization, the Global Network Initiative, the companies will set out their principles for doing business in countries that restrict free speech online. Other participants in the initiative include human-rights campaigners and socially responsible investors, including Human Rights First, the World Press Freedom Committee and Human Rights Watch.

The three companies and more than a dozen other groups announced the new organization and a framework negotiated over the past two years during a news conference Tuesday. "We believe that by acting together -- with other companies and with groups of investors -- we have a better chance of modifying the behavior of governments than if we do it individually," said Robert Mahoney, deputy director of the Committee to Project Journalists.

Google, Yahoo and Microsoft dominate the search engine market and also host blogs, Web mail services and forums that are used around the world, putting them in a powerful position to influence the discovery and discussion of information. Human-rights advocates and other critics have accused them of abusing this position to aid censorship in some countries, by editing search-engine results or providing information about the identities of journalists, bloggers and other critics of government policies.

The Global Network Initiative published a set of guidelines for companies to follow when faced with government requests to censor information on the Web or unveil the identity of a user. The guidelines put out Tuesday are a first step in a continuing process to deal with government censorship issues, and the focus will be on working together to create better responses to government requests, said Colin Maclay, acting executive director of the Berkman Center for Internet and Society at the Harvard Law School.

"The truth is that no one in the world has the answer to these problems, and there's not just one answer," Maclay said.

The guidelines call for Internet companies to assess the human-rights impact of the government requests and to require that governments follow established legal processes when looking to restrict freedom of expression.

A new Web site, globalnetworkinitiative.org, will include information about the guidelines and the new initiative by late Tuesday, said Leslie Harris, president and CEO of the Center for Democracy and Technology (CDT), one of the groups coordinating the efforts.

The guidelines will help Internet companies focus on human rights and will open up their internal processes to outside review, said Michael Samway, Yahoo’s deputy general counsel. The groups involved have talked about companies creating internal teams that look at human-rights issues in addition to business and legal issues, he said.