Are they lurking in the darker reaches of YouTube?

Or delivering a series of 'pokes' and other greetings on the social networking site Facebook?

Nope. Today's kids aged 12 and under are likely to be whiling away their online hours playing games on sites you have never heard of.

The most popular website for young, web-savvy Britons, Stardoll.com, was set up by a 60-year-old Finnish woman who wanted to pass on the art of knitting clothes for a doll - in a modern context.

Top ten websites for young British internet users

• Where the web kids are

• Focus: Brave new world

• Electronic Arts to give away video games online

Related Links

• Focus: Brave new world

• Electronic Arts to give away its games online

• Microsoft opens the Xbox to amateur game writers

Second in the top ten for under 12s was an arctic-themed virtual world in which players adopt a virtual penguin and march it round cartoonish-looking venues such as 'the beach', 'the theatre', and 'school'.

Stardoll.com, which makes money by selling items of virtual clothing for about 50p each, and ClubPenguin, which offers a subscription service, were singled out in a survey of young Britons' internet habits conducted by Nielsen Online, the analyst.

Other sites favoured by the youngest web users were the online portals of the kids TV channels Cartoon Network and Nick, and Lego.com - which lure in their audiences with a mixture of video content, games, and competitions.

In the 12-to-17 age group, Bebo, the youth-focused social networking site, BBC schools, the learning portal, and Frengo, a lesser-known service which connects a users to social neworking sites they are signed up to, fared the best.

The Nielsen study of 40,000 British internet users examined which sites had the highest concentration of users of a particular age group.

Bebo, for instance, had 919,000 unique users aged 12-17, who made up 19 per cent of its audience. Only Frengo (26 per cent) and Runescape, an online role-playing game (25 per cent) had a higher "density" of 12-17s.

Entertainment industry experts said that interactive games were by far and away the most popular type of content with under 12s because they allowed for a more immersive experience than video.

"In focus groups, we often ask kids what they would like to do most with our shows, and the answer is always: we want to be in the cartoon," said Ian McClelland, director of digital development for EMEA at Turner Broadcasting - which owns Cartoon Network. "Games allow that kind of experience."

A new Asian-themed game called Chop Socky Chooks: Trouble In The Wasabi Warehouse, which was co-produced with Aardman - the company behind Chicken Run - will launch on the Cartoon Network next month.

Sites which offer games that could be played for free on the web, such as FreeOnlineGames were also beginning to show through because the increased powers of web browers such as Internet Explorer.

"Not only has the quality of online games gotten a lot better, but web browsers now allow you to have a very rich experience of a game without having to download anything - and that's a big psychological barrier," said Mike Reid, a former partner in the technology group at 3i, the private equity firm.

"In turn internet companies are discovering new business models, such as showing users ads while they play games, and charging them for 'virtual goods' such as clothing," he said.

The popularity of sites within a particular age group is difficult to measure because several sites - such as Google and Yahoo! - are so ubiquitous that regardless of the age category they will come out top.

Nielsen's tactic of measuring a percentage of audience - rather than the outright number of users - within a given age category is an attempt to get around this problem, but sites must have a minimum base of users - 14,000 - in order to be considered.

Click here for the most popular websites for kids and teens

Explore Tech & Web

• Personal Tech

• The Web

• Gadgets & Gaming