[Lynne]

You would need to add several (and go look up radius css because you need to add different stuff for different browsers - this is just for one browser):

.postbit, .postbitlegacy, .eventbit {
     border-radius: 10px 10px 10px 10px;
}

.postbit .posthead, .postbitlegacy .posthead, .eventbit .eventhead {
     border-radius: 10px 10px 0px 0px;
}

.postbit .postfoot .textcontrols, .postbitlegacy .postfoot .textcontrols, .eventbit .eventfoot .eventcontrols {border-radius: 0 0 10px 10px;}