Continents – Countries – Cities,
and many others ….
Upload it to any document library in your site (assuming its hidden from users, you will not want users to modify it and give you a shock)
Now in the custom list New Form/Edit Form, add a Content Editor Webpart and make it hidden
Edit the WebPart properties and click on “Source Editor”
Paste the following line –
ChildDropDownListFieldControl child = (ChildDropDownListFieldControl)
There you go !!!