Guide to bullying
Online bullying is when children or teenagers use the web, or mobile phones or any other technology to threaten, tease or embarrass another young person.
Nasty messages are just one form of online bullying.
Often bullies set up a website or group on a social media website like Facebook and then ask other people to join in and comment about a person or images of them.
But it can also include things like emailing someone a virus on purpose, posting personal information where it shouldn't be or calling them names when playing a game together online.
Bullies on the web can't cause physical pain, but because of the way we now live our lives - with mobile phones and lots of internet use - they can be very hard to avoid.
Another big difference between normal bulling and online bullying is that it's often difficult to work out who the cyberbullies are, as they can hide behind fake names.
What can you do to stop it?
The best advice is to avoid the methods used by online bullies.
That means staying away from websites they use and blocking email addresses or mobile numbers that send nasty messages. Regularly check and clean your 'friends' lists on social networking sites too.
Find the 'report abuse' or 'block sender' options on your favourite websites.
Changing your username may also help and don't give out personal details such as your mobile number, address or email online.
Protect your password too to keep your files and information safe.
You should also report the bullying to the people running the website, technology service or your mobile phone service provider.
Keep evidence - callers and mailers can be traced. But also remember that sites you've created and emails you've sent can be traced back to you months or years later too.
And as with all bullying, telling an adult it's happening is REALLY important too.