[bes]

<style>
.cl {width:100px; height: 40px; border: 1px solid red;}
#di {border: 1px solid blue;}
</style>

<div id="idd">
	<button>add</button>
	<div class="cl">1</div>
	<div class="cl">2</div>
<div>

<script>
window.onload = function () {
	document.getElementById('idd').onclick = function (e) {
		e = e || event;
		var target = e.target || e.srcElement;
		if (target == this.children[0]) {
			var el = document.createElement('div');
			el.innerHTML = this.children.length - 1;
			el.className = 'cl';
			this.appendChild(el);
		} else 
		if (target.className == 'cl') {
			if(!document.getElementById("di")) {
				var el = document.createElement("div");
				el.id = "di";
				el.innerHTML = "div";
			} else {
				var el = document.getElementById("di");
			}
			target.appendChild(el);
		}
	}
}
</script>