<!DOCTYPE html>
<html>
<body>
<span>span1</span>
<span>span2</span>
<span>span3</span>
<h1 id="h1_id">H1</h1>
<script>
var sp = document.getElementsByTagName("span")[0];
var hd = document.getElementById("h1_id");
hd.insertAdjacentElement("afterend", sp);
</script>
</body>
</html>
<!--
span2 span3
H1
span1
-->