Timing can be an important factor, with Chinese censors blocking access to some websites around politically sensitive dates, such as the June 4 anniversary of the 1989 Tiananmen massacre and the Chinese Communist Party Congress, a political confab held once every five years to choose top leaders and set policy that is now underway in Beijing.
Access to a search engine can also be blocked if a user searches for a politically sensitive word, such as a search for information on the banned Falungong religious sect.
Tracking the ebb and flow of censorship efforts can be a challenge, as access to sites can be blocked and opened, seemingly by whim. On Wednesday, Wikipedia remained blocked in China and access to YouTube was shut off. But censors eased off on other sites, opening up access to Google's Blogspot blogging service and permitting users to view pictures on Flickr, which had been blocked even though the site was accessible in China.
Even when websites are accessible in China, there can be moments when sites cannot be reached. For example, one of the Chinese internet users in Beijing contacted for this story said he was unable to reach Google.com three days ago. Attempts to reach the site were not redirected to Baidu, and Google has been accessible during the last couple of days, he said.
While the Chinese government may not be redirecting search-engine traffic to Baidu, censors did this in 2002, just before the previous Party Congress opened in Beijing. At that time, censors cut off access to Google and redirected traffic to several local search engines, including Baidu. However, the rerouting did not affect all users and did not appear to be done at a national level, analysts said at that time.