To find out what site is default, go to point your browser to your External IP address

http://x.x.x.x

If this is not the one you want to display by default, then change the order that they are loaded by apache.

First make sure that you do not have any VirtualHost definitions in here

nano /opt/local/etc/http/httpd.conf

Then number your virtualhosts/*.conf files like so:

001-example.com.conf
002-another.com.conf

then restart apache

sudo svcadm restart apache