function update() {

var html = document.getElementById("html");
var css = document.getElementById("css");
var code = document.getElementById("code").contentWindow.document;

document.body.onkeyup = function(){
  code.open();
	code.writeln(html.value+"<style>"+css.value+"</style>");
	code.close();
  };
document.addEventListener("DOMContentLoaded", function(){
  code.open();
  code.writeln(html.value+"<style>"+css.value+"</style>");
  code.close();
  });
};

update();