css/CSS2/zindex/z-index-004.xht

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <title>CSS Test: Z-index set to zero prefixed with a minus sign</title>
        <link rel="author" title="Microsoft" href="http://www.microsoft.com/" />
		<link rel="reviewer" title="Gérard Talbot" href="http://www.gtalbot.org/BrowserBugsSection/css21testsuite/" /> <!-- 2012-07-03 -->
        <link rel="help" href="http://www.w3.org/TR/CSS21/visuren.html#propdef-z-index" />
        <link rel="help" href="http://www.w3.org/TR/CSS21/visuren.html#z-index" />
		<link rel="match" href="../reference/ref-filled-green-100px-square.xht" />

        <meta name="assert" content="The property z-index set to '0' prefixed with a minus sign is read as value '0'." />
        <style type="text/css">
            #div1
            {
                background: red;
                height: 100px;
                left: 0;
                position: absolute;
                top: 0;
                width: 100px;
                z-index: -0;
            }
            #div2
            {
                background: green;
                height: 100px;
                left: 0;
                position: absolute;
                top: 0;
                width: 100px;
            }
            #wrapper
            {
                position: relative;
            }
        </style>
    </head>
    <body>
        <p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
        <div id="wrapper">
            <div id="div1"></div>
            <div id="div2"></div>
        </div>
    </body>
</html>