<!DOCTYPE html>
<html>
<body onload="loaded()">
<span style="position: relative; top: 100px">foo<br>
<span id="ins-point">bar</span></span>
<script>
function loaded() {
var insPoint = document.getElementById("ins-point");
var span = document.createElement("span");
span.style.position = "absolute";
span.style.top = 0;
span.appendChild(document.createTextNode("abs"));
insPoint.insertBefore(span, insPoint.firstChild);
}
</script>
</body>
</html>