If your teens are on social networks, the scariest part is "not knowing." Not knowing who their online friends are, not knowing whether they've been cyberbullied, not knowing much of anything about their online social lives (which you do know occupies them nearly every waking moment).

But a new study by the Pew Research Center sheds some much-needed light on what teens are really doing -- and how they feel about their experiences -- when they disappear into Facebook and MySpace.

Teens, Kindness and Cruelty on Social Network Sites, conducted by Pew's Internet and American Life Project, found that a majority (69%) of social media-using teens report that their online peers are mostly kind to each other on social network sites. While the findings show that cyberbullying persists, most teens say that their online experiences are positive.

And there's more to calm your concerns:

• 65% of social media-using teens say they personally have had an experience on a social network site that made them feel good about themselves
• 58% say they felt closer to another person because of an experience on a social network site
• 80% of teens who've witnessed mean and cruel behavior have come to the defense of a targeted social networking friend

These statistics indicate progress -- and speak to the value of digital citizenship education and anti-cyberbullying efforts by both parents and schools (including Common Sense Media's own programs). Still, 88% of teen social-media users has witnessed cruelty on social media. And if your teen is one of the 25% whose social networking experience caused them to have a face-to-face argument, or one of the 15% who've personally experienced someone being mean or cruel to them, you know that there's more work to do.

Fortunately, there is something you can do, and the report is clear that "parents are the most often cited source of advice and the biggest influence on teens' understanding of appropriate and inappropriate digital behavior." Here are some ways to help your teens have positive social networking experiences:

Talk to your teens about responsible, respectful online behavior. When the teens in the study were asked to describe how people should act online, they used words like "respectful," "caring," and "mature." Another phrase the teens used to define responsible behavior: "Don't put it all out there." Talk to your teens about keeping private stuff private.

Friend your teen -- but don't forget them! 80% of parents whose kids use social media have friended their kids, but 18% of those teens still experienced a negative social networking experience. So keep checking in with your teen about what's going on.

Remember that social networking is just life for teens. The regular ups and downs of teen life will invade social networks. Be sensitive to when the online drama crosses the line from normal teen problems to deeper issues, and step in if necessary.