<style>
    #float {
        float: left;
        width: 50px;
        height: 50px;
        background-color: green;
    }
</style>
<div style="font: 20px ahem; width: 220px; border: solid blue; -webkit-font-smoothing: none;">
    <span id="span">Lorem</span> ipsum dolor sit amet, consectetur <div id="float"></div>adipiscing elit.
</div>
<div style="z-index: -1; position: absolute; top: 91px; left: 11px; width: 50px; height: 50px; background-color: red;"></div>
<script>
    document.body.offsetTop;
    document.getElementById("span").innerText = "lorem";
    document.getElementById("float").style.height = "25px";
</script>