Forcing child to obey parent's curved borders in CSS

Question

I have a div inside of another div. #outer and #inner. #outer has curved borders and a white background. #inner has no

Answer 1

What would be wrong with this?

#outer { 
    display: block; float: right; margin: 0; width: 200px;
    background-color: white; overflow: hidden;
}
#inner { background-color: #209400; height: 10px; border-top: none; }

#outer, #inner{
    -moz-border-radius: 10px; 
    -khtml-border-radius: 10px; 
    -webkit-border-radius: 10px; 
    border-radius: 10px; 
}