<style>
    #target { color: green; margin-top: -100px; }
    #target:before { display: block; 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>
