How can I determine if iptables is blocking traffic to my site?

On some Linux systems, a built-in firewall known as "iptables" is enabled.  This keeps novice or lazy users from opening up all the services of their computer to outside attacks. 

However, when testing or working on a network already protected by a good (and well managed) firewall, there's not really a need to have this on. 

You can view iptables rules with this command (you need to be logged as root):

service iptables status

Turn off iptables with this command:

service iptables stop

You can turn it back on with:

service iptables start