The sentence was handed down to Patrick Green, 33, at Aylesbury Crown Court on the day that a website was launched to alert parents to the dangers of online chat rooms.
Green, who pleaded guilty at an earlier hearing to two counts of indecent assault, four counts of unlawful sex with a minor and one count of attempted unlawful sexual intercourse with a minor, was branded a "predator" by Judge Christopher Tyrer.
Green also admitted eight counts of possessing indecent photographs of children.
Experts fear that Green is only one of a number of paedophiles who are using the internet to seek out their victims.
The teenager's family was so shocked by what happened they have backed a new website, spelling out the dangers young people face online.
Green spent weeks gaining the trust of the child through chat room conversations and emails, before finally talking to her on her mobile phone and arranging to meet.
He denied two charges of abduction which were ordered to remain on file.
Warning to parents
Chatdanger.com - being launched on Tuesday - warns that there is no way of knowing who you are talking to in a chatroom.
It advises that teenagers should never give out personal information, such as email addresses, and should never arrange to meet a chatroom friend.
The website has been set up by Childnet International, a charity which aims to make the internet a safe place for children.
Childnet Director, Nigel Williams, said: "We hope that parents look at it because there is an area there that will explain all the detail of how chat actually works, and why kids are so interested in it.
"There's also an area for teens themselves to see the sort of things they can do."
'Net smart'
People are warned to look out for chatroom users who initially claim to be one age then change it, or who try to drive a wedge between the child and their family through sympathy and flattery.
But children's charities fear that, as more and more young people use chatrooms, there will be more and more cases of paedophiles stalking their victims online.
John Carr, internet adviser for NCH Action for Children, said: "Children have got to be streetwise in cyberspace. They've got to be net smart. They've got to think of the internet like a modern city.
"They've got to know the people they might meet there aren't necessarily all that they claim to be and won't always have the best of intentions towards them."
He fears if people are not vigilant then the UK will find that, like the United States, it is facing hundreds of cases where paedophiles have used the internet to lure children.