u cant do it directly. dor some reason golives webdav implementation wont work with .mac...at least 6's didnt. havnt tried CS yet.
there is a way to trick it though.
mount your idisk and turn on FTP access and file sharing. it should let you publish your localhost/volumes/idiskname
or something like that.
i wrote an article about it on my old site...but its just my blog now.
im sure you can get it to work.