URL to test host headers - LilyCollin

I am trying to implement host headers in a series of web sites on IIS 6.0.  I
haven't yet set up DNS entries (I believe I do this by specifying the IP
address and the relevant host header name).  But I just wanted to test the
host headers were working.

I have tried using a URL in the format http://hostname:80:hostheadername
from another computer on the network but I get an error of Windows cannot
find 'http://hostname:80:hostheadername'. Check the spelling and try again.

If I try the URL http://localhost:80:hostheadername from the web server I
get the following error: The page cannot be displayed
The page you are looking for might have been removed or had its name changed.

Can I not check the host headers in this way?  Do I need to create a DNS
entry or make a manual change to the Hosts file to test the host headers?

Thank you.