Border radius

Hello to all who stumble upon this topic!

I need help, i can not figure this out.
I need rounded edges at top of my page and at bottom of my footer,
here is the image of what i want:
Image

I am using thesis theme and in a custom.css i have this code:

.custom #content_area { background: url( images/Bottom_texture.jpg ) repeat; }

.custom #content_area .page { background: url( images/Bottom_texture.jpg ) repeat; }

.custom #content_box { background: #eaddcc; border-radius:5px; -moz-border-radius:5px; -webkit-border-radius:5px; }

.format_text {padding-left: 100px; padding-right:100px; padding-top:20px; }

When i put a border-radius:5px; it round up whole content area, i want just top to be rounded. Is there some code that tells html that i only want a top to be rounded of page and bottom of footer?
Maybe something like this: border-radius-top:5px.