代码示例:(标识:css3_outline-offset)
<!DOCTYPE html>
<html>
<head>
<style> 
div.ex1 {
  margin: 20px;
  border: 1px solid black;
  outline: 4px solid red;
  outline-offset: 15px;
} 

div.ex2 {
  margin: 10px;
  border: 1px solid black;
  outline: 5px dashed blue;
  outline-offset: 5px;
} 
</style>
</head>
<body>
<h1>outline-offset 属性</h1>

<div class="ex1">这个 div 有 4 像素的红色实线轮廓,位于边框边缘外 15 像素处。</div>
<br>
<div class="ex2">这个 div 有 5 像素的蓝色虚线轮廓,位于边框边缘外 5 像素处。</div>

</body>
</html>
运行结果: