By Mark Ward
Technology Correspondent, BBC News website
In less than 10 years China has gone from a net newcomer to the country with the world's second-largest online population.
The net is taking off in China
The first international internet data from China started travelling across the net in 1994, yet now the country has more than 100m net users
That puts its second only to the US with its 185m web users. But China looks set to pass that within a few years - especially when you consider that China's net users represent barely 8% of its population.
If Chinese net use grows to the levels seen in many Western nations, it could end up with 750m people regularly going online.
But currently the experience of the average Chinese net user differs greatly from that of many in the West.
Part of the net's allure to Western users is the sense of freedom it gives them to look at, read, and say almost anything they want.
By contrast, Chinese net use is much more circumscribed.
Much has been made of the so-called Great Firewall of China that censors what people see using technology built in to the country's basic net infrastructure.
The Chinese authorities have used several methods to "sanitise" what people see online, according to a report from US firm Dynamic Internet Technologies, which watches net use in the country.
On the most basic level, the firewall blocks net addresses hosting webpages that the authorities would rather people did not see. Anyone trying to visit these pages gets told that the page cannot be found or does not exist.
More sophisticated firewall technology spots when people are searching the web for particular words and hijacks their session to stop them getting the information.
Also China has changed its core net address books, known as Domain Name Servers, which tell a user's computer where to find a particular webpage on the net.
The sites blocked by these techniques include the many dealing with taboo subjects such as Tibet and Falun Gong as well as the BBC News website, search engine Google, sex sites such as Playboy and many blogs.
There is also an entire department of the police force that patrols online.
But despite the sophistication of these technologies, they are not infallible.
To begin with, blocking an entire net address can stop people getting at all the information on a webpage, some of which might be relatively neutral.
Numerous reports show that many of China's net users know how to get around these restrictions.
Many Chinese people use net cafes because PCs are costly
The web addresses of proxies, that help users see banned pages, are well known. Many activist organisations in the West help pass on the addresses of these pages and set up new ones when old ones are shut down.
Equally there are programs produced by firm such as Dynaweb and Ultrareach that let people see banned sites and get e-mail from overseas.
The technology also has some embarrassing holes.
For instance a version of the Google website called Elgoog (Google spelled backwards) that accepts queries also written backwards apparently slips through the firewall.
But what does make a difference is the responsibilities the Chinese authorities heap upon native net service firms, said Xiao Qiang, head of the China internet project at the University of California Berkeley and a contributor to the China Digital News blog.
"The government makes every digital enterprise, online hosting service and commercial portal accountable for what they publish," he said. "If they don't, they won't be able to do business in China."
This stands in contrast to many Western nations which regard net service firms as common carriers, which like postal services, are not responsible for what customers do.
Net cafes have to abide by a strict series of guidelines that govern where they can be sited, what services they can offer and how they must monitor what customers do.
Those that do not comply are shut down. In 2004, more than 47,000 net cafes were shut for breaking these laws.
This leads to a lot of self-censorship and a willingness by private firms to co-operate with government monitoring of what people do online, said Julien Pain, head of the internet freedom desk at Reporters Without Borders.
"The intention is to clear the web of subversive material," he said.
Surveillance is easy via the net warn activists
The monitoring of comments posted in chat rooms and on bulletin boards is quite aggressive, said Mr Pain.
Now, he said, thanks to automatic censoring systems undesirable postings only last a few minutes.
Less than 18 months ago, such posts would survive for up to 30 minutes, he said.
The consequences of posting subversive information, be it about Tibet, Falun Gong, or even Sars can be severe.
This week Amnesty International released a report that highlighted the number of people imprisoned for championing human rights in China. Many were jailed for posting information online.
Currently 54 people are thought to be in jail because they were judged to distributed "illegal" information via the net.
Many activists used to think that the more people that were online the harder it would be to censor, said Mr Pain.
But, by contrast, censorship of political debate in China seems to be getting more effective.
"We are talking about software that's really efficient," he said, "and when you have 100 million or 200 million people it does not make any difference."
The resources that the Chinese government puts in to monitoring dwarfs the efforts of the activist groups working to combat it.
Said Mr Pain: "Surveillance is much easier in cyberspace than in the real world."