<style type="text/css">
div.thin {
margin:3px; padding:3px;
border:thin solid silver; /* 細め */
}
div.medium {
margin:3px; padding:3px;
border:medium solid silver; /* 通常 */
}
div.thick {
margin:3px; padding:3px;
border:thick solid silver; /* 太め */
}
div.border10 {
margin:3px; padding:3px;
border:10px solid silver; /* サイズ指定 */
}
</style>
<div class="border10">
<div class="thick">
<div class="medium">
<div class="thin">border-width</div>
</div>
</div>
</div>