Make container of elements with margin in-between elements but not the container?

Make container of elements with margin in-between elements but not the
container?

Container #666 has margin: 20px; overflow: hidden;.
Nodes #333 have margin: 20px 0 0 20px; float: left;.
The result is:

Example, http://jsbin.com/owejal/3/edit.
However, the intended result is:
container with 20px margin,
children with 20px margin in-between, but not with the container.