percent-top-value-with-relative-position.html

<html>
<head>
<style>
#wrap {
    width: 100%;
    height: 100%;
}

#outside_frame {
    position: relative;
    top: 50%;
}
/* safari hack */
html*#outside_frame {
    position: absolute;
    left: 50%;
    top: 50%;
    margin-left: -480px;
    margin-top: -254px;
    background-color: purple;
}
</style>
</head>
<body>
<div id="wrap">
    <div id="outside_frame">This test passes if the text is rendered in the middle of the page.</div>
</div>
</body>
</html>

chromium/third_party/blink/web_tests/fast/css/percent-top-value-with-relative-position.html