<html>
<body style="font: 1em/1 Ahem, sans-serif;">
<style>    
#test
{
    color: blue;
    display: table-row;
}
</style>
<div id="test">
ABCD
</div>
<div style="font-size: 800%; color: green">
EFGH
</div>
<script>
    document.body.offsetTop;
    var test = document.getElementById("test");
    test.style.fontSize = "800%";
</script>
</body>
</html>