<html xmlns="http://www.w3.org/1999/xhtml" style="white-space: pre;">
<head>
<style>

#f:first-letter { }
#g:first-letter { float:left; }

</style>
<script>

function boom(id)
{
  var text = document.getElementById(id).firstChild;
  text.splitText(2);
  document.documentElement.offsetHeight;
  text.splitText(0);
}

</script>
</head>
<body onload="boom('f');boom('g');">


<div id="f">

X</div>

<div id="g">

X</div>


</body>
</html>