Domain Alias: Is defined by our control panel as an edit or addition to the Host headers in IIS. This allows you do a Url redirect after you add an "A" record like http://Example.domainname.com then use an asp redirect to point http://Example.domainname.com to any collection of files and folders. This is much the same as a Sub Web without the extra overhead of adding a separate entry in IIS. This is why we purposefully have set our sub-webs available lower to reduce the number of entries on a machine.