BeardmoreWeb

I have had this issue numerous times before but finally I found where the iWeb files live.  Before re-installing OS X or moving to a different machine, copy the file that is located at /users/CURRENT USER/Library/Application Support/iWeb/

The file will be a .sites2 file and when you copy that over to a new machine or install iWeb will have all the information, files and settings that it needs, including .mac information.