[monolithed]

<style type="text/css">
#div1, #div2 {
	border: 1px solid #DDDDDD;
	margin: 50px auto;
}

#div1 {
	width: 200px;
	height: 100px;
}

#div2 {
	background: #FFFFFF;
	width: 100px;
	height: 50px;
}
</style>
	
<script type="text/javascript">
window.onload = function(){
	var div1 = document.getElementById("div1");
	var div2 = document.getElementById("div2");
	div2.onclick = function(){
		div1.style.background = (div1.style.background == '#000000') ? '' : '#000000';
	};
};
</script>

<div id="div1">
	<div id="div2"></div>
</div>