Under the Multisite Options you can map the Site Address when the user registers...
On the form itself can I write in the first part of the URL ie http://www.example.com/ (then the form box), so the user just types in the last part of the URL instead of the whole url?
This is hard to explain but right now http://www.example.com/sitename has to be typed when "sitename" would be easier.
This is confusing on the users part