I'm trying to layout part of a site designed with rounded corners. I've tried several ways, but became frustrated when this almost worked: Demo

All four corners are visible in FF, but the bottom-left corner has vanished in IE6. As the layer containing the bottom-left corner is higher in the nested layer stack than that containing the left margin, I could understand if it were the left margin that didn't display, however this makes little sense to me.

Anyone have any blinding insights?