China watchers, get your scorecards out: Google's YouTube is blocked, Wikipedia is still blocked, but for the moment, Google blog site Blogspot.com is available and some pictures from Yahoo's Flickr photos can once again be viewed.

China-based users accessing YouTube since Wednesday afternoon began receiving the dreaded "The server at www.youtube.com is taking too long to respond," the typical response when a user attempts to view a site that has been blocked.

Google's blog site, Blogspot, is currently available after being blocked in June. An unblocking of the site last year led to the availability of a Shanghai-based foreign blogger known as Chinabounder, whose blog recounted the author's sexual exploits with Chinese women while working as an English teacher. The posts ultimately led to an unsuccessful hunt for the author and a temporary closing of the blog. Google did not respond to a request for comment on YouTube's block and Blogspot's availability.

Photo site Flickr is once again displaying most of its photos, after its pictures, but not the site itself, were blocked in June. The Flickr photo block was the most obvious indicator that China's blocking technology goes beyond simple domain restrictions, but could target subdomains. Even now, some Flickr images remain blocked while others display. For example, searching for the term "Beijing" from a China-based computer displays the larger photos on the left, but the avatars of users do not load.

China regularly blocks access to Web sites that it finds objectionable, including those dealing with politically sensitive subjects such as the Falun Gong religious cult and independence for Taiwan and Tibet, along with some pornographic sites. However, while both Playboy.com and Penthouse.com are available, the British Broadcasting Corp.'s news site is not. The Chinese government does not announce or comment when a site is blocked or made available.

The current blocking may be related to the Communist Party Congress, which began Oct. 15 in Beijing and ends Sunday. Held once every five years, the meeting is the Chinese government's most important political gathering, used to create five-year plans, which are the bedrock of China's centrally planned economy. It is also often used to reshuffle government positions or for leaders to consolidate their power.

"It is never clear why the authorities block or unblock access to Web sites," said Jeremy Goldkorn, editor of Danwei.org, a Beijing-based, English-language media blog. "With the 17th Communist Party Congress currently taking place in Beijing, China's media regulators and media organizations are on high alert for anything the Party might find objectionable."