Image caption The Daily Mail has mastered the art of the long website headline

The Daily Mail has overtaken the New York Times to become the world's most visited newspaper website, according to online tracking service Comscore. The biggest increase in readers has been in the US - so how did this very British institution do it?

There is something compellingly simple about MailOnline. No fancy site navigation, picture carousels or slideshows - just a front page with stories and pictures. Thousands of them.

The New York Times claims it is still the world's most popular newspaper website, because the Mail figures include visits to sister sites.

But let that not detract from the British newspaper's achievement in going from nowhere to 45.3 million unique visitors a month in just five years. What is its secret?

1. Celebrity news

MailOnline's success in the United States has been partly built, most pundits agree, on celebrity gossip. It is a very different beast from its more strait-laced print sister, even though it shares a lot of content with it.

Celebrity journalist and author Jo Piazza believes it is much imitated by rival US-based gossip sites.

Speaking in frank terms, she says: "Until we started seeing this influx of gossip websites here in the United States, the media was very ass-kissy towards celebrities, whereas the Daily Mail has never done that.

Image caption Celebrity stories are key to MailOnline's growing popularity

"A lot of the gossip blogs and the gossip websites look to the Daily Mail for how to package celebrity news. They are just that good at it."

People are going to click on stories that take celebrities down a notch over ones that hold them up on a pedestal, says Ms Piazza, a former gossip columnist on the New York Daily News.

"That's why the Mail is so smart and that's why their traffic is going up and up.

"Almost every celebrity journalist I know has it on their RSS. It doesn't typically break celebrity news, but they are really good at spinning it. They're really good at aggregating the content. They are great at putting a snappy headline on it. No one captions a celebrity picture better than the Daily Mail."

But it's not all showbiz. On Friday, its lead story was about conditions in a Chinese factory.

2. Unorthodox design

MailOnline breaks just about every web design rule in the book, according to internet usability consultant Jakob Nielsen.

The hundreds of stories competing for attention on its front page, the fact that it rarely links to external sites from news stories and the way it breaks up text with enormous pictures all count against it, says Mr Nielsen.

But, he adds, "you don't have to spend a lot of time working out how the site works, it's very simple" and the traffic figures speak for themselves.

One reason for the immense length of the MailOnline home page, he suggests, is that it could boost search engine rankings, by fooling them into believing stories "must be important because they are linked off the front page".

3. Big pictures

Another ingredient to its success is its big, bold use of pictures.

A series of large images, one below the other, interrupted by a few lines of text, is a successful staple of many MailOnline articles.

There are plenty more pictures in the right-hand side column, which is a series of celebrity stories promoted in a few words and an enticing image.

But even this feature on the right is occasionally sacrificed, when a story requires even bigger picture treatment, like when a key freeway closed in Los Angeles.

4. Long, long headlines

News websites long ago got wise to the trick of packing their headlines with common search terms so that they would appear towards the top of the Google rankings.

What does the Mail say about its success? "MailOnline showcases all that is best about British popular journalism. It is produced using traditional journalistic values and skills that are as old as Fleet Street itself and illustrates not just how its legacy can survive but how it can prosper as a world-beater in the digital age." Martin Clarke, MailOnline publisher

But MailOnline has taken Search Engine Optimisation to a whole different level. Its headlines are so long they are like mini stories in themselves, says Jakob Neilsen.

One side-effect of this approach is that readers will probably not feel "disappointed" when they click on a story, which may help to build loyalty to the site, he argues.

But Ken Doctor, an expert in the economics of internet news, argues that there is little brand loyalty in a world where people fire stories around the web at their friends on Twitter and Facebook.

"I bet most people don't even know they are reading the Daily Mail or what the Daily Mail is," he says.

Using long headlines packed with celebrity names may attract the passing internet browser but it does not necessarily build name recognition or attract advertising cash.

"They are very proficient at search engine optimisation - they get up high in search rankings - and that will generate great amounts of traffic but it's not producing high amounts of revenue," says Mr Doctor, who last year carried out a study of advertising per unique user at the world's biggest newspaper sites.

5. Concentrating on its web content

"It's an entirely different entity to the print edition," says Ms Piazza.

"They created this as a business model for what works online and they know what's going to get eyeballs and traffic, and bring in advertisers, and they have created a website around that, not around their print edition."

Unlike most other newspapers, with "integrated" newsrooms, the Mail has kept its web and print journalists separate.

It has launched a US edition of its website, and taken on staff in New York and Los Angeles to help it compete head-on with US newspaper and showbiz gossip sites.