The moves follow criticism from parent groups and authorities who fear the site had not gone far enough in providing protection for younger members.

Staying safe

The adverts are part of an ongoing campaign by the US Ad Council and the National Center for Missing & Exploited Children.

They aim to educate parents about what measures they can take to protect their children, and to raise awareness among teens on creating safe online relationships.

The adverts will also air on Fox television, radio and across NewsCorp's network of websites.

"One of the things we're trying to persuade kids to do is not to give out personal details online, don't advertise where they are and who they are," said Ernie Allen of the National Center for Missing and Exploited Children.

"The person with whom they may be interacting may not be who they say they are."

MySpace, which began as a site for music fans, has grown rapidly in popularity among teens as a social networking hub.

Just over one fifth of the website's users are registered as under 18.

Although it forbids minors under 13 from joining, and provides special protection for those aged 14 and 15, children are still able to lie to get around the restrictions.

Last month, two men were arrested in the US over sex charges after they allegedly used MySpace to meet two girls aged 11 and 14.

Security chief

The Fox Corporation has also appointed Hemanshu Nigam to oversee safety, education, privacy and law enforcement for MySpace.

Mr Nigam, who is currently the director of Consumer Security Outreach & Child Safe Computing at Microsoft, will take up his new post on 1 May.

He has previously served as a federal prosecutor against internet child exploitation for the US Department of Justice.

MySpace says it also attempts to protect minors by flagging up members likely to be under 14. It said more than 250,000 flagged profiles have been deleted since the site began.

In addition, teens aged 14 and 15 have restrictions imposed on their pages, so that only those on their friends' list can view their profile.

Allen Weiner, an internet analyst for Gartner, said the site suffers because of its popularity.

"People are going to find nefarious things to do with anything that draws such a huge audience.

"I think MySpace is actually doing a pretty decent job in terms of security," he added