代码示例:(标识:css_zindex)
<!DOCTYPE html>
<html>
<head>
<style>
img {
  position: absolute;
  left: 0px;
  top: 0px;
  z-index: -1;
}
</style>
</head>
<body>

<h1>这是标题</h1>
<img src="/logo.png" width="188" height="267">
<p>由于图像的 z-index 为 -1,它将被置于文本之后。</p>

</body>
</html>
运行结果: