#1

(pronounced as separate letters) Short for demilitarized zone, a computer or small subnetwork that sits between a trusted internal network, such as a corporate private LAN, and an untrusted external network, such as the public Internet.
Typically, the DMZ contains devices accessible to Internet traffic, such as Web (HTTP ) servers, FTP servers, SMTP (e-mail) servers and DNS servers.

The term comes from military use, meaning a buffer area between two enemies.
Source : http://www.webopedia.com/TERM/D/DMZ.html

#2 Did you try DLink Technical Support?

#3 Are you on *DSL modem or Cable Modem?