There is a problem with the DNS configuration inside your network. What are the name servers on your workstations set to? Is there a gateway or internal DNS server?
Both these are Internet Explorer's way of telling you that it either can't resolve the domain, there's no authorative data for it, or any number of other problems.
Same with me - works fine.
You don't need to do this. Your workstations should do a normal DNS query to your DNS cache (at your ISP, locally, whatever) which will return the address of your IIS server, which will then serve up the page. Try opening up a Command Prompt and typing: ping www.gwinto.co.uk
What happens then? If you get an IP address and packets coming back, it's not a DNS issue.