If you have received this error while you were restarting the Apache2 server on Debian Squeeze:

/etc/init.d/apache2 start
Starting web server: apache2apache2: Could not reliably determine the server’s fully qualified domain name, using 127.0.1.1 for ServerName

To fix this problem  you need to edit the /etc/apache2/apache2.conf.

1. Open the /etc/apache2/apache2.conf file with your favorite editor.

vim /etc/apache2/apache2.conf

2. Now add the following line:

ServerName localhost

3. Restart apache2 server:

 /etc/init.d/apache2 restart
Restarting web server: apache2 … waiting ..

Now your problem is gone. Enjoy.