#top {
background-position:top right;
margin-bottom: 15px;
}

#top div {
position:absolute;
left:0px;
top:0px;
width:20px; /* top corner width */
margin-left: -20px;
height:100%;
_height:1600px; /* arbitrary long height, IE 6 */
background-position:top left;
}

#bas {
background-position:bottom right;
margin-top:15px;
}

#bas div {
position:absolute;
left:0px;
top:0px;
width:20px; /* bottom corner width */
margin:0 0 0 -20px;
height:100%;
_height:1600px; /* arbitrary long height, IE 6 */
background-position:bottom left;
}