appendChild(), createElement()

<div id="sandbox">
</div>

var greeting =document.createElement("span");

greeting.style.backgroundColor="yellow";

greeting.innerHTML="Hello World!";

document.getElementById("sandbox").appendChild(greeting); 


document.getElementById("sandbox").appendChild(document.createElement("hr"));
var link = document.createElement("a");
link.href="http://ajaxpatterns.org";
link.appendChild(document.createTextNode("More Ajax Stuff..."));
document.getElementById("sandbox").appendChild(link);