I have just installed Apache 2.2.17, and I am using it first time.
Now when I try to start the server using the command service httpd start it gives me
service httpd start
I was NOT getting the ServerName wrong. Inside your VirtualHost configuration that is causing this warning message, it is the generic one near the top of your httpd.conf which is by default commented out.
Change
#ServerName www.example.com:80
to:
ServerName 127.0.0.1:80