A majority of U.S. adults are uncomfortable with Web sites using a person's online activity to deliver customized content, a study released Thursday showed.

However, Harris Interactive found that people became more comfortable after they were presented with Web-site privacy and security policies recommended by the Federal Trade Commission.

Based on a nationwide survey of more than 2,500 U.S. adults, the study found that six in 10 respondents were skeptical when Web sites like those from Google, Yahoo, and Microsoft used visitors' online activity to tailor advertisements or content based on their hobbies or interests. A quarter of the respondents were "not at all comfortable," and 34% were "not very comfortable."

The remaining 41% were split between the 7% of people who were "very comfortable," and the 34% who said they were "somewhat comfortable."

Columbia University professor and study designer Alan F. Westin said the study showed a disconnection between Web sites and Web users. The former argues that users are likely to consider free e-mail accounts, the lessening of irrelevant ads, and other benefits as worth the trade-off of having their activities tracked. "Though our question flagged this position, 59% of current online users clearly do not accept it," Westin said in a statement.

Researchers found a change in attitude after the FTC-recommended privacy/security policies were introduced. The recommendations include greater disclosure on use of data and consumer control, limited data retention, and opt-in consent for material changes to existing privacy promises and for use of sensitive data.

If these conditions were applied, then 55% of the respondents to Harris' survey said they would be more comfortable with Web companies using information from visitors' activities.