An In-Depth Discussion of Virtual Host Matching http://httpd.apache.org/docs/current/vhosts/details.html
How to disable default VirtualHost in apache2? http://serverfault.com/questions/114931/how-to-disable-default-virtualhost-in-apache2
How to disable the default document root in Apache? http://serverfault.com/questions/705169/how-to-disable-the-default-document-root-in-apache
How do I setup a PTR record with my exisiting domain name? | DigitalOcean https://www.digitalocean.com/community/questions/how-do-i-setup-a-ptr-record-with-my-exisiting-domain-name