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<html><body><h1>This is a Heading</h1><img id="img1" src="bulbon.gif" style="position:absolute;left:0px;top:0px;z-index:-1;width:100px;height:180px;"><button type="button" onclick="myFunction()">Alert stack order</button><p>Default z-index is 0. Z-index -1 has lower priority.</p><script>function myFunction() { alert(document.getElementById("img1").style.zIndex);}</script></body></html>