The television, radio and website messages, being broadcast throughout January, aim to make parents and youngsters aware of how to surf the web safely.
There is also a new set of guidelines for internet service providers, who offer chat and instant messaging services.
These include measures such as the provision of clear warning information, and ways for children to report problems online.
Tips for parents
The aim is to stop paedophiles "grooming" youngsters online.
An estimated five million youngsters under 16 have private access to the internet, and nearly half of 16-year-olds use chatrooms, according to research published last year.
Home Office Minister Hilary Benn said he hoped the campaign would give parents and children "basic safety messages", without demonising the internet.
"They're exactly the same messages, in essence, that we give our children about people they might meet in the street - don't go with strangers," he told BBC Breakfast.
Tips for young surfer
"It's not intended to add to worry, it's about giving our children the information they need to protect themselves.
"The internet is a great tool, it opens up all sorts of possibilities and we don't want to scare people about using it, we just want to make sure that when you use the internet you do so safely."
Children's charity Childline said the advice was very welcome, as it received "hundreds" of calls a year from children who had been "very distressed by experiences they've come across on the net".
Chief executive Dr Carol Easton told BBC Radio 4's Today programme: "They're putting themselves at risk and they've been abused as a result, so the dangers are real."
She compared the advice to teaching a small child how to cross the road - saying the guidelines would alert and empower young surfers.
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The internet is a great tool... we just want to make sure that when you use the internet you do so safely
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Hilary Benn
Home Office Minister
Nigel Williams, chief executive of internet safety charity Childnet, told Breakfast the guidelines for the ISPs were an "excellent first step".
But he said they must be "followed through" with close monitoring of all chatrooms, to make sure they were adhered to.
And he pointed out that many chatrooms were run from outside the UK, by companies who may take no notice of the guidelines.
The guidelines were welcomed by the major teachers' union ATL, which on the same day published advice for teachers on "safe learning with the internet".
"The last thing teachers want to do is to be killjoys in the face of the exciting learning opportunities that the internet offers, but teachers do worry about the real risks that young people face," said Gwen Evans, Deputy General Secretary.
But there was criticism from the Professor of Sociology at Kent University, Frank Furedi, who said the campaign was a waste of money.
'Scare stories'
"Sensible parents would tell their children how to behave in different circumstances. We don't need expensive gestures by the government... parents can inform them," he told Today.
TALKING POINT
How safe is the net for kids?
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The internet is not, nor ever will be, a safe place for children to roam unguided.
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Matt Smith, West Yorks
He blamed the media for creating an unnecessary culture of fear about the internet with "too many scare stories".
"Every new technology has been portrayed as a new danger to children, from the time of the introduction of the bicycle to the introduction of movies and cinemas.
"With the internet this has been amplified because quite often parents and adults are less able to surf the net than their children."