代码示例:(标识:dhtm_zindex2)
<html>

<head>
<style>
img.x
{
position:absolute;
left:0px;
top:0px;
z-index:-1;
}
</style>
</head>

<body>

<h1>这是一个标题</h1>
<img class="x" src="/static/demo/images/eg_bulbon.gif" /> 

<p>默认 z-index 是 0。Z-index -1 有更低的优先级。</p>

</body>
</html>
运行结果: