I had Apache2 installed and it works fine and I can access my web page from anywhere but yesterday I cannot access it. I tried to restart Apache2 and it gave the following message:"Could not determine the server's fully qualified domain name, using 127.0.0.1 for ServerName". I edit the apache2.conf file to add the ServerName and restart apache2, the message was gone but I still cannot connect to the server. The error message returned by my name server was: "The following error was encountered:
Connection to 86.143.222.247 Failed

The system returned:

(110) Connection timed out

The remote host or network may be down. Please try the request again."

I also lost SSH connectivity at the same time, which had been working for the past three months. Everything just suddenly falls apart. Are there anybody give me a clue on what had happened?

Unless your ISP provides you with a static IP address you need to configure "dynamic DNS" to ensure that your system can be accessed. Otherwise your ISP can assign your computer a different IP address at any time, breaking remote access.

The other possibility is that you have a router or firewall issue, which is preventing any successful connection to the system.

Thanks a lot, I've checked my router, it was the port forwarding issue and is now fixed.