Parents have received the warning before, but we fear too few have listened.

Most of us who are parents think our children are wonderful. They bring great joy to our lives - even though they can be a challenge at times.

But, parents, there is a pretty good chance your child is doing things on Facebook, Twitter and other social media websites that you don't know about.

And you can't protect them if you don't know what they're up to.

When attached to a computer or smartphone, Annie might not behave like the lovely child you raised. And, Bobby ... He might be sharing pictures you'd hope he'd never see, and befriending people he doesn't even know.

That's exactly why you need to be nosy and ask your kids what they're doing on the Internet. It's not about being an overbearing parent; it's about keeping your child safe from harm.

Here are two cases in point from last week in Indiana.

• A 16-year-old girl allegedly drove 60 miles from Monticello to LaPorte to beat up a 17-year-old girl for posting rumors about her on Facebook. Police say the teen knocked the other girl down and kicked her. She's now being held on charges of battery, curfew violation and resisting law enforcement.

• Indiana's law banning registered sex offenders from using Facebook or other social networking sites that can be accessed by children was ruled unconstitutional by a federal appeals court.

The court said the state was justified in trying to protect children but that the "blanket ban" went too far by restricting free speech.

We know there were local sex offenders on Facebook even while the ban was in place. A statewide ban is only as good as how it well it is being enforced.

We can't say this enough: Know what your children are doing online. Look at their Facebook fans and Twitter followers. Make sure they use strict privacy settings, and demand they give you all the usernames and passwords to any account they have set up online.

Nothing is more important than protecting our young people. Without proper guidance and limitations, they can easily stray from the path we have provided for them. That's why parents must be diligent in making sure online activity is monitored and kept as safe as possible.