A visitor left flowers on the Google logo outside the company's China headquarters in Beijing on Wednesday. (Gemunu Amarasinghe/Associated Press)

Type "Falun Gong" in Chinese into Google's search engine from Beijing, and the web browser suddenly becomes unresponsive for about a minute. Make the same search from Hong Kong, and you'll get plenty of links to the spiritual movement banned by the Chinese government.

Internet users in mainland China and Hong Kong now share the same Google search site, but their experiences continue to widely differ, particularly on topics deemed sensitive by China's Communist leaders. The difference is that the government, rather than Google, is now doing the censoring.

The findings in a recent Associated Press test offer insights into the sophistication with which China uses its complex "Great Firewall" to filter its citizens' online view of the world.

Recent searches for taboo topics from Beijing generally produced "page cannot be displayed" errors. The user's browser stops working for about a minute, longer if one tries to access forbidden sites in quick succession. In other words, it's not just the links to those sites that don't work; the results don't come back at all.

Yet the filters aren't exact, and English-language sites have a greater chance of slipping through, partly because the government is more concerned about the vast majority of citizens who speak only Chinese. And even as the Great Firewall blocks Twitter and sensitive blog postings, excerpts do show up on Google's search results page.

A large network of filters

The findings illustrate how China's vast government-run network of web filters works. When a user enters a sensitive term in a search, it triggers a brief blockage that affects subsequent searches — even those on innocuous topics — by that user or anyone else at the same numeric internet address. That can be one computer or an entire cybercafé.

Chinese-language searches for missing Chinese activist lawyer Gao Zhisheng, jailed Chinese dissident Liu Xiaobo, Chinese President Hu Jintao and "June 4 incident" — known elsewhere as the 1989 Tiananmen Square crackdown — all led to the web browser in Beijing hanging for a minute or longer.

Before Google killed its mainland search service Monday and redirected "Google.cn" traffic to its existing Hong Kong-based site, Google returned censored results with a note explaining that some items had been removed. Google needed to comply with Chinese laws, but it wanted users to know about the omissions in hopes they would pressure their government to lift restraints.

But Google announced Jan. 12 that it was no longer willing to censor those results after it discovered it was the target of hacking attacks originating from China. Unable to reach agreement with the ruling party on running an uncensored search service, Google decided to send mainland users to Hong Kong, a Chinese territory that is semiautonomous because of its past as a British colony.

Some Google searches produce the same results whether from Beijing or Hong Kong. Among them: "Michael Jackson" and "March 14 incident," which refers to the 2008 anti-Chinese riots in the Tibetan capital, Lhasa. "Taiwan" also produced no difference in search results, despite tensions with a region that China considers its own.

In other cases, results appear the same, but the text ads alongside them differ. A recent search for "iPhone" in Hong Kong produced two sponsored links, for the Apple store in Hong Kong and for Vodafone, while the one in Beijing led to the mainland version of Apple's home page. In most cases, though, the mainland version of the search produced more ads than in Hong Kong.

Google routinely uses a computer's numeric internet address to determine the visitor's location and adjust search results and ads accordingly. Visiting the U.S.-focused Google.com site from Geneva, for instance, often takes you automatically to the Swiss version of the site at Google.ch. Even within the United States, sites for some local businesses may show up higher or lower in the results depending on where you are.

Thus, despite Google's decision to give mainland users the Hong Kong site, at Google.com.hk, visitors from Beijing still see differences having nothing to do with China's filters.

With the change, Hong Kong's site began displaying search results in the simplified Chinese characters that are used in mainland China, but Hong Kong visitors still get a page in the traditional Chinese script, with links to versions for English or simplified Chinese.

Beijing visitors get the simplified version first, and their Hong Kong page looks much like the old Google.cn, with colourful, animated icons offering quick links to video, shopping and other popular features.

Mainland users denied YouTube

The Google-owned online video leader, YouTube, is typically blocked on the mainland. In Beijing, searches on a separate Google video service are directed to a Google.cn site where the company is still censoring results. Video, music and maps are among the features that Google continues to operate in China. In Hong Kong, however, video searches go to the Hong Kong site, where results are not censored.

Meanwhile, Hong Kong users can reach a China-only music service, but unless you're on the mainland, you get this advisory when you try to listen to a song: "Music streaming/download services are not available in your region."

Despite the pervasive reach of the Great Firewall, mainland Chinese can use Google's Hong Kong site for a glimpse of material that is usually blocked.

Consider a search for "Obama." One recent search from Beijing produced a page leading with news stories about the U.S. president, but the results page also included recent posts by people on Twitter, a social-messaging service that is blocked in China.

In a Chinese-language search for "Tibet," Google includes excerpts from such blogs as Invisible Tibet, which is written by the well-known Tibetan poet and activist Woeser and is usually blocked in China.

Not surprisingly, attempts to access the blog from the search page failed. By comparison, a search for Woeser's blog on the Chinese search site Baidu.com produced one line: "The search results could involve content that fails to comply with the relevant laws, regulation and policies and are not displayed."

Meanwhile, a search for "Tibet" in English shows links to Free Tibet, the International Campaign for Tibet and other activist sites.

The Great Firewall isn't an exact science, but it's meant to keep most of the sensitive content from most of the citizens most of the time.