Chatting to your mates online can be loads of fun, but kids are being urged to make sure they stay safe on the web.
Events are being held across the world to mark Safer Internet Day, to try and raise awareness of the dangers of the internet.
One of the things kids are being warned about is cyber-bullying, which is when bullies use the web, or mobile phones, to send nasty messages to someone.
One study found that almost half the kids surveyed had experienced it.
Researchers for the charity Beatbullying spoke to almost 2,500 young people about cyber-bullying.
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Tips on beating cyber-bullying
One in ten admitted they had sent a bullying message to someone else.
John Mangelaars from Microsoft said kids were getting better at using the web because lots of them were using it to keep in touch with their friends.
But he said research showed kids still needed to learn more about staying safe.
"They still need help and guidance on how to tackle emerging issues such as online bullying," he said.
Seventeen social networking sites have pledged to do more to protect the young people that use them, for Safer Internet Day.
And lots of schools are taking part to try and teach children ways of staying safe online.