我第一次设置了Amazon EC2 Ubuntu 16服务器。
使用已发布的公共IPv4 IP地址，我已将ssh插入服务器并安装了灯架。
但是，当我将IP地址粘贴到浏览器中时，出现以下错误：
Error
The requested URL could not be retrieved
Error: Access to the web site failed
Why you are seeing this:
The web filter could not display the requested site.
Possible reasons could be:
The web site denied you access, or the web filter received no reply from the site.
Internet connectivity issues might be preventing the website from sending or receiving traffic.
If this problem persists, please ask your administrator to:
Check access to the specific site - the HTTP error code is 504: Gateway Timeout.
根据我在网上看到的内容，此时我应该从服务器上看到默认的apache网页。
任何人都可以阐明这个问题吗？