重启apache2出现_default_VirtualHost overlap on port 80, the firsthas提示,该怎么处理

重启apache2出现_default_VirtualHost overlap on port 80, the firsthas提示
我刚刚重启apache2发现_default_ VirtualHost overlap on port 80, the first has的 提示。我的bbs也是php的，现在访问就出现400请求错误。请问怎么回事呀。我没有改过配置呀？ 
系统是linux

------解决方案--------------------------------------------------------
端口冲突。。。