cannot access to web site After installation

[kunimii]

I install Pleask 8.0 trial version (for 1 domain name) on DELL Server, Model: sc1425,
OS: Freebsd 6.0. After completely installation and setup, I change to the new ip address.
It could work when i enter the website via ip address directly. Then I change the DNS for
my domain name. After DNS updated, someone could enter the website but someone could not.
The process I do when I change the new ip address as follows;


First, I change ip on my os (FreeBSD) in /etc/rc.conf , /etc/resolv.conf and /etc/hosts

reboot

I click reread IP in IP Management of PLESK control panel and change client to new IP

I can directy access my web via IP now.

Then i update new IP to my domain and it update already.
Anyway , i cannot access web via my domain name.

I ask to Admin of company where I co-locate the server, he could access web via my domain name.
Is it relate to he is on same network of my server?

I ask my friend who use another internet account of other ISP. All of them could not access the web site via my domain name.
Including my friend in another country.

What's wrong with them? Do I setup more on FreeBSD and PLESK?


Thank you very much.

kunimii.