Chinese micro-blogging sites Digu and Zuosa were both shut down for maintenance on 21 July. Wen Yunchao, a well-known blogger, said having two sites close on the same day indicates pressure from authorities for them to shut down. He said the timing of the closures was probably related to the 10-year anniversary on 22 July of the banning of the Falun Gong spiritual movement. Read more here