Facebook chief executive Mark Zuckerberg this week denied that he signed over 84 percent of the social-networking site to a man for $1,000.

"If we said that we were unsure, that was likely taken out of context, because I think we were quite sure that we did not sign a contract that says they have any right to ownership over Facebook," Zuckerberg said during an interview with ABC's Diane Sawyer.

Last month, Paul Ceglia sued Zuckerberg over what Ceglia said was a contract that Zuckerberg signed to hand over 50 percent of Facebook for $1,000. The contract also allegedly included a clause that would add 1 percent ownership for each day passed Jan. 1, 2004 that TheFacebook.com was not live.

Facebook initially said that the case was "frivolous," but a Facebook lawyer later told a judge that she was "unsure" whether the signature on the contract belonged to Zuckerberg. The 26-year-old CEO is now apparently confident that he did not sign the document.

Zuckerberg sat down with Sawyer to commemorate the fact that Facebook has now reached 500 million users, but he also touched on the site's privacy issues, assorted legal battles, and – most importantly – the site's plans for a "dislike" button.

"We've made mistakes for sure," Zuckerberg said about the company's privacy policies. "I think they're a lot better."

When asked why all information is not private by default, Zuckerberg reiterated his opinion that Facebook is "set in a way that helps people share." He said "the right thing is to make it so certain information is always private."

A movie detailing the origins of Facebook – and the ensuing legal battles with Zuckerberg's co-founders – is set to hit theaters later this year. When asked if he would have done anything differently, Zuckerberg said yes, but also pointed out that he was only 19 at the time, so mistakes were bound to happen.

"I think instead of making the mistakes that I made I would've made different mistakes," he said.

Why did Facebook turn down a $1 billion offer from Yahoo in 2006? "We just felt that doing that and going down that path would not help us build Facebook out to what it would be," he said.

Finally, Zuckerberg said the much-requested "dislike" button is "something that we would definitely think about," but he did not commit to adding it to the site.