Dear Till, thank you for your reply.
Ok, I could assign a temporary domain to the website that resolves already to my server, but then there's another problem (I'm referring to situation (2) as described in my previous post). Ok the client will see his site being developed at this temporary domain, but when everything's finished I'll need to move the site to this client's account and his domain (that will start pointing at my server once everything is done).
If the site in question is a simple html site, then it's OK - I'll just copy the contents. But what if it's a complex site based on some CMS (Content Management System), for example, Joomla? With MySQL databases, etc?
So my question is - is there a way in ispconfig to move a site fully from one domain (in this case, temporary) to another domain? (I understand that 'move sites' tool in ispconfig only moves a site from one client to another).