The European Commission is telling teens to be cautious when posting personal information on social networking sites.
It's Safe Internet Day around the globe and the EU is also telling companies to do more to protect teens' privacy.
The Commission says 50 percent of European teens give out personal information online. It also found that only a third of social networking sites responded to user reports asking for help, and 11 of 22 social networks allow private profiles to be visible through search engines.
"I expect all companies to do more," said Viviane Reding, EU Commissioner for Information Society and Media. "Minors' profiles need to be set to private by default and questions or abuse reports have to receive quick and appropriate responses. The internet is now vital to our children, and it is the responsibility of all to make it safe."
U.S. online safety advocates are also urging teens to "Think B4 U Post."
The Family Online Safety Institute says young kids and teens should be taught "digital citizenship skills" to help them share information in intelligent ways.
"While there is a recognition that there must be a base-line of safety -- using filters for younger kids and monitoring and privacy settings for the older ones -- the emphasis is now placed on education, media literacy and a new kind of civics," FOSI CEO Stephen Balkam wrote in a Huffington Post op-ed. "It's time for kids of all ages to understand and value the rights of free speech and assembly (ie, connecting through social networking and other means) as well as an expectation of privacy and safety."