Can't get server to work on the web need some help

[kadi]

hello everybody
this is my first try with linux server so i am no expert, but i learned some new things with linux, i used debian etch 4.0r1server also i followed the perfect setup for debian etch instructions and thanks alot to mr/Falko without this help it will take me may be at least a few months to set it up.
I have ISPConfig installed and i setup the DNS on it for the domain ,i checked the box Create DNS , the domain is registered with a company (registerar) , also i have to mension that i am using a Router with a cable modem.
now I can see the site (index) on the localhost but i can't see it or access it
outside the server on the web or the internet, i tried so many computers to
get to the site from outside but it does not work.
I ping the dns from network tools and it works fine also if i enter the ip in browser from outside computer on the web it comes on with shared IP page but if i use the name www.mydomain.com it syas cannot find page.
I ping the dns [ns1.mydomain.com] from another computer it says Request timed out.
I don't know what i am missing , i even reinstalled the OS 3 times to clean the system and still didn't work.
so i am not sure what could be the reason, is it the files like hosts, hostname, network interfaces, or could be from ISPConfig ?
I attached some files in zip format it may help.
Thanks very much for help in advance it will be appreciated.