Six teenagers aged 14 and 15 have been arrested for allegedly using a social networking website to organise fights between rival gangs across Derby.
Police said they acted on intelligence the youngsters used Bebo to arrange the fights between November and January.
The youths were questioned about the fights and their postings on the web.
They were released on police bail, but five will face final warnings and be asked to sign acceptable behaviour contracts, said a force spokesman.
Nobody was injured in the confrontations but police urged parents to be vigilant over what their children are looking at on their computers.
Bebo agreed to take the material relating to the fights in Derby off its website. The youths concerned were interviewed by police officers this week.
A police spokesman said: "We have taken what we think is early preventative action before it gets serious.
"Some people think the internet is private but it's a public place and if they are posting messages which could lead to disorder then that's something we will take a keen interest in."
A spokeswoman from Bebo said: "Unfortunately, anti-social behaviour is an aspect of the society we live in.
"Content which comes to our attention that contravenes those terms is immediately suspended and investigated."