今天用Magento安装一个插件失败了，再刷新前台，后台都打不开，网站标题显示503错误，只有magento connect页面能打开，错误提示如下：
Service Temporarily Unavailable
The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.
解决方法非常简单了，只需要把你magento网站根目录下的maintenance.flag文件删掉就可以了