Border Radius Tab

今こんな感じでタブ作ってる。
Code
html
<ul class="shift_box"> <li class="current"><a href="">タブだよ</a></li> <li><a href="">タブだよ</a></li> </ul> <div class="contents"> <h2>タイトルだよ</h2> </div>
* {
margin: 0;
padding: 0;
border: 0;
}
body {
background: #fff;
font: 30px sans-serif;
padding: 40px;
}
ul {
list-style: none;
}
.contents {
padding: 12px 20px;
border: 4px solid #d9d8d6;
border-radius: 4px;
background-color: white;
margin-bottom: 20px;
}
h2 {
background: none;
border-left: 6px solid #E7BE00;
border-radius: 0;
color: #3F2500;
font-size: 18px;
line-height: 22px;
padding: 0 0 0 10px;
}
.shift_box {
margin-bottom: -4px;
overflow: hidden;
}
.shift_box .current {
background: #fff;
border-top: 4px solid #d9d8d6;
border-right: 4px solid #d9d8d6;
border-left: 4px solid #d9d8d6;
}
.shift_box .current a {
width: 160px;
border-bottom: 4px solid #fff;
}
.shift_box li {
background: #d9d8d6;
border: 4px solid #d9d8d6;
border-radius: 4px 4px 0 0;
float: left;
margin: 0 8px 0 0;
text-align: center;
width: 160px;
}
.shift_box li a {
color: #4C2C00;
font-size: 16px;
font-weight: bold;
padding: 9px 48px;
text-decoration: none;
}