IIS problems- connecting only when online

I am trying to set up IIS on this new computer, but I'm having trouble with it. On my old 'puter I didn't have any problem, I just set it up and it worked.

When I'm in work, I connect to the LAN and get net access of that. The old 'puter had no net access.

So basicly my question is, why did all the functions on my site work fine on IIS on my old 'puter, but on the new one, it only works when I'm connected to the net, and how to I change this?

I think I have all the setting ok, and the site is working now (as in on IIS and when I'm connected), but I can't work on personal stuff in here, and I cant connected to the net at home.

The error I get is a

Page Cannot be Displayed

Cannot find server or DNS Error
Internet Explorer

And all the stuff in between 404 I think.

sometimes i had this problem and it had to do with some settings within my network, so check the main machine and then check the child machines and see what could be causing the problem.