The NewMacUser.com website presents a number of articles concerning MobileMe a.k.a. .Mac. This one explains how to use iWeb to support multiple web sites.
He starts out with the basics:
In order to have MobileMe (me.com) host multiple domains you will need to have a basic understanding of how to use domain forwarding. I want to let everyone know upfront that this process may or may not be supported by apple, but it works very well.
For my example I will be using my domain registrar GoDaddy.com, your register may differ bit in the process but for the most part it will be the same.
He uses a couple of domains as an example and uses different templates from iWeb.
See the full article here: http://newmacuser.com/multiple-domains-with-mobileme/
