Fijate si te sirve:
Código PHP:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Documento sin título</title>
<style>
#p{ width:200px; height:200px; background:#F00; position:relative}
#h{ width:50px; height:50px; position:absolute; left:75px; top:75px; background:#36F}
</style>
</head>
<body>
<div id="p" onclick="ob=event.srcElement || event.target;if(ob==this)alert(this.id)">
<div id="h"></div>
</div>
</body>
</html>