Like the insertBefore method, this inserts a node after the specified one. This requires the prototype.js framework.

Object.extend(Element.Methods, {
	insertAfter: function(parent,newNode,referenceNode) {
		return parent.insertBefore(newNode,referenceNode.nextSibling);
	}
});
Element.addMethods();

parentNode.insertAfter(newNode,referenceNode);