The website of a leading liberal magazine is back online after being blocked for several days - seemingly in an error by the internet service provider. The website of Yanhuang Chunqiu (yhcqw.com), one of the most outspoken publications on the mainland, could not be accessed last weekend, prompting speculation of a clampdown on political expression days ahead of the 20th anniversary of the June 4 crackdown. However, Wu Si, the editor-in-chief of the monthly magazine, investigated the incident on Monday and found this was far from the truth. He said the magazine's webmaster contacted the ISP to discover which government department had ordered the shutdown and why. 'One of the ISP's staff told my colleague that two postings on the forum provided by our website had crossed the line and caused some trouble,' said Mr Wu, who would not disclose the name of the ISP. Mr Wu said the magazine did not know who posted articles on its forum. They could be domestic users or someone overseas, and the quantity of new comments each day made it impossible to monitor everything. 'In a bid to avoid further impact and play it safe, the ISP chose on Friday evening to shut down our website instead of deleting the controversial posts, which was not what it was instructed to do by any official censors,' Mr Wu said. After reading one of the forum posts, Mr Wu agreed it was too politically sensitive, though he would not divulge the subject matter. 'My guess is that the ISP overreacted,' said Mr Wu. The editor added that he believed the department for overseeing online affairs had reprimanded the ISP over the shutdown and ordered it to restore normal service immediately. Service was restored on Monday afternoon. Mr Wu was confident the incident would not affect publication of the magazine's print edition. As one of the mainland's most high-profile liberal publications, any suppression of Yanhuang Chunqiu would have raised concerns of an effort to stifle dissenting voices in this sensitive period, which besides June 4 includes the 60th anniversary of the founding of the People's Republic in October. Late last year, the Ministry of Culture forced a reshuffling of the editorial board after the magazine published an article about late party chief Zhao Ziyang. Mr Wu was appointed editor in February.