案例：javascript案例     状态：可编辑再运行    进入竖版
 运行结果　
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<html>
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<head>
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<style type="text/css">
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#img1
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{
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position:absolute;
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left:0px;
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top:0px;
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z-index:-1
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}
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</style>
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<script type="text/javascript">
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function changeStackOrder()
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{
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document.getElementById("img1").style.zIndex="1";
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}
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</script>
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</head>
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<body>
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​
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<h1>This is a Heading</h1>
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​
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<img id="img1" src="/img/eg_bulbon.gif">
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​
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<p>Default z-index is 0. Z-index -1 has lower priority.</p>
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​
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<input type="button" onclick="changeStackOrder()" value="Change stack order" />
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​
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</body>
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</html>
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​