Internet safety: One girl's tale of danger online
Newsround's special programme Caught in the Web and looks at how to stay out of danger online.
Sonali's been speaking to one girl who got into serious trouble online after making friends with a man who asked her to do things she was uncomfortable with.
She told her sister about it - and now the man's in prison.
To hide her identity we've used someone else's voice to tell her story.