<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8>
<script>
function boom()
{
var e = document.getElementsByTagName("mo")[0];
e.setAttribute("style", "position: absolute; top: 0px;");
document.documentElement.offsetHeight;
e.setAttribute("style", "position: absolute; top: 100px;");
}
</script>
</head>
<body onload="boom();">
<math><mo>boom!</mo></math>
</body>
</html>