一，效果图。
二，代码。
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>CSS Border(边框)</title>
<style>
p.one {
border-style: solid;
border-width: 5px;
border-color: red;
border-top-style: dotted;
border-right-style: solid;
border-bottom-style: dotted;
border-left-style: solid;
}
p.two {
border-style: solid;
border-width: medium;
border-color: #98bf21;
}
p.three {
border-style: solid;
border-width: 1px;
}
</style>
</head>
<body>
<p class="one">Some text.</p>
<p class="two">Some text.</p>
<p class="three">Some text.</p>
<p><b>Note:</b> The "border-width" property does not work if it is used alone. Use the "border-style" property to set the borders first.</p>
</body>
</html>
参考资料:《菜鸟教程》