CSS로 둥근 모서리 구현하기

<style>
.rtop, .rbottom{display:block; background: #FFFFFF;}
.rtop *, .rbottom *{display: block; height: 1px; overflow: hidden; background: #9BD1FA;}
.r1{margin: 0 5px}
.r2{margin: 0 3px}
.r3{margin: 0 2px}
.r4{margin: 0 1px; height: 2px}
</style>
<div id="container" style="background: #9BD1FA">
<b class="rtop">
<b class="r1"></b> <b class="r2"></b> <b class="r3"></b> <b class="r4"></b>
</b>
<p>
CSS로 둥근 모서리 구현하기</p>
<b class="rbottom">
<b class="r4"></b> <b class="r3"></b> <b class="r2"></b> <b class="r1"></b>
</b>
</div>