Briefly unavailable for scheduled maintenance. Check back in a minute.
升级时没有备份数据库，出现这个时立马就faint了
网上查了google，登陆ftp删除了根目录下的 .maintenance 文件 就ok了。
Cause of the Maintenance Message
During an automatic upgrade, WordPress places a file in the blog root directory called “.maintenance” to prevent visitors from being confronted with ugly, bro...