Thanks Ralph - have tried to get this information via my client, but it's not forthcoming. Anyways, it was a worth a try here
It should at least be easy enough to get the name of the web hosting company. They will want to confirm with the site owner that info can be shared with you, but then you can get all the info you need from the host. Don't give up: it will happen.
Domain tool Whois lookup
Netcraft internet exploration (use the what's that site running search box)
BuiltWith (sometimes provides info on backend)
Andrew Wasson | www.lunadesign.org
Principal / Internet Development