It has 17,000 members worldwide and if you put teen dating into Google, it comes up first in the search.
It has almost 1,700 members in the UK, a quarter of which are under-16.
Many of them are pictured in swimwear or underwear.
It also has more than 150 male members who are listed as older than 40.
Older man 'warning'
The NSPCC says there is a "huge danger" the site will be used by adults to make illegal contact with younger children.
The charity says the site encourages children to give out personal details and photos in a sexualised way.
Zoe Hilton from the charity wants it shut down.
She said: "Many people who may be searching for children will not be honest about their age.
"There doesn't seem to be any evidence on this site that they are actually moderating what is going on at all.
We state pretty clearly in the terms of service, specifically not to give out any personal information at all. It's up to them if they want to be open
MyLOL.net owner Anthony Lipari
"Sites like this one should be taken off the internet."
Newsbeat discovered online conversations between older men and teenage girls.
In one, a man who says he's 23 swaps contact details with a 14-year-old.
Another of the charity's criticisms is the lack of controls to stop under-13s using the site.
An 11-year-old girl called Bethany who uses it told Newsbeat random people have contacted her but "if anyone's older than me I don't normally talk to them".
Her mum Tammy told Newsbeat she's aware she uses it and checks who she talks to.
She said: "The whole internet, there's going to be people who are portraying themselves as things they're not.
"That's a risk you've got to teach them about rather than trying to avoid it completely."
There are 'report abuse' buttons on people's profiles.
There is also an advice page warning about the dangers of chat rooms and fake users, but you have to click through four pages before you can see it and it's not simple to find.
Newsbeat tracked down the site's owner, an 18-year-old from Australia, Anthony Lipari.
He bought it recently and says he hasn't had time yet to make all the changes he wants to.
He also defended it: "We state pretty clearly in the terms of service, specifically not to give out any personal information at all. It's up to them if they want to be open."
When asked about the dangers of older men contacting young children he replied: "What can we do about it? We can't actually find out if they're paedophiles or anything. They're just guys using the site."
He said there's already been a case where a 40-year-old man was harassing a girl on the site.
Anthony Lipari said: "They can report problems if they find guys are abusing them or sending any sort of messages."
But after being made aware of all the concerns with the site Mr Lipari said security would be improved.
The changes should take a few months.
A spokesperson for the Child Exploitation and Online Protection centre, CEOP, said: "The issue is whether the content is illegal or not.
"We are aware of the site but won't say if it's under investigation."