Los Angeles  - A law firm has released details of what was supposed to be a confidential 65-million-dollar payoff by Facebook to plaintiffs who claimed the social networking site was based on their ideas.

The payment was made by Facebook last year to smaller rival ConnectU, which had accused Facebook Chief Executive Mark Zuckerberg, a fellow Harvard University graduate, of stealing their ideas to create his site. The ConnectU founders claimed to have hired Zuckerberg while all were students at Harvard University to create a college dating site.

Details of last year's settlement were supposed to be confidential. But law firm Quinn Emanuel inadvertently revealed the amount in a marketing newsletter.

The settlement figure should not have a huge impact on the privately owned Facebook, which was valued at 15 billion dollars when Microsoft made a 500-million-dollar investment in 2007. However, though the site has grown significantly since then its valuation has likely dropped due to the negative economic environment.

Peter Calamari, a lawyer representing ConnectU, told legal publication The Reporter that the release of the details was inadvertent.

"Our PR people released something, and it didn't get caught by the people who knew," he said. "We had a policy against commenting or talking publicly about this case." (dpa)