<style>
#target { color: green; margin-top: -100px; }
#target:before { display: table; content: "A"; }
#target:first-letter { font-size: 200%; }
</style>
<body style="font-family: Ahem; -webkit-font-smoothing: none;">
<div style="font-size: 100px; color: red;">A</div>
<div id="target"></div>
<script>
document.body.offsetTop;
document.getElementById("target").style.fontSize = "50px";
</script>
</body>