body {background-color:#000;}

.curvedBox
{
width:300px;
}
.curvedBox .r1, .curvedBox .r2, .curvedBox .r3, .curvedBox .r4
{
background-color:#fff;
display:block;
overflow:hidden;
height:1px;
font-size:1px;
}
.curvedBox .r2, .curvedBox .r3, .curvedBox .r4
{
border-width:0 1px;
border-left:1px solid #fff;
border-right:1px solid #fff;
}
.curvedBox .r1 {margin:0 6px;}
.curvedBox .r2 {margin:0 3px;}
.curvedBox .r3 {margin:0 2px;}
.curvedBox .r4 {margin:0 1px;height:2px;}

.curvedBox .content
{
background:#fff;
border-left:1px solid #fff;
border-right:1px solid #fff;
padding:0 5px;
}