Do you have Friendly Error Messages turned off in IE? What kind of "can't
display" is this -- the 404 kind or the "missing server" kind?

Are you trying to hit the site from the server, or from another client
machine? If the former, is LoopbackCheck disabled? If the latter, does the
client have access to the server on the correct port?

Are both Web Applications on Port 80? If they are then you need to have
either pre-created the web sites in IIS to use different IP addresses (not
likely) or created them using host headers. Otherwise IIS won't know which
web site to access when you hit the server on Port 80.

If you did use host headers, then you also need to enter the host header
that you used in to the DNS server. Otherwise you won't be able to find the
web site and will get the error you are describing.

Finally, if you used a different port number then you need to add the port
number to the URL when you try to access the site.