<html>
<head>
<style>
body { margin: 0 }
div { width: 100%; height:100%; }
.div1 { background-color: green; position: absolute; z-index: 21233443232232 }
.div2 { background-color: red; position:absolute; z-index: 10 }
</style>
</head>
<body>
<div class="div1"></div>
<div class="div2"></div>