Does the 960-plugin in compass auto-clear floats? I would assume so, but I'm having trouble with my layout right now, so I am guessing I have to explicitly clear it using the compass clear mixin?
Looks like it doesn't have it. I checked the source code and saw this:
=grid-container
margin-left: auto
margin-right: auto
width: $ninesixty-grid-width
no clearfix in sight