body {background-color:#000;}

.curvedBox300
{
width:300px;
}
.curvedBox300 .r1-300, .curvedBox300 .r2-300, .curvedBox300 .r3-300, .curvedBox300 .r4-300
{
background-color:#fff;
display:block;
overflow:hidden;
height:1px;
font-size:1px;
}
.curvedBox300 .r2-300, .curvedBox300 .r3-300, .curvedBox300 .r4-300
{
border-width:0 1px;
border-left:1px solid #fff;
border-right:1px solid #fff;
}
.curvedBox300 .r1-300 {margin:0 6px;}
.curvedBox300 .r2-300 {margin:0 3px;}
.curvedBox300 .r3-300 {margin:0 2px;}
.curvedBox300 .r4-300 {margin:0 1px;height:2px;}

.curvedBox300 .content
{
background:#fff;
border-left:1px solid #fff;
border-right:1px solid #fff;
padding:0 5px;
}