event.srcElement
<head>
<script>
function clicked(){
alert(event.srcElement.id);
}
</script>
</head>
<Body>
<DIV id="001" onclick="clicked()">area 1</DIV>
<DIV id="002" onclick="clicked()">area 2</DIV>
</Body>
<head>
<script>
function clicked(){
alert(event.srcElement.id);
}
</script>
</head>
<Body>
<DIV id="001" onclick="clicked()">area 1</DIV>
<DIV id="002" onclick="clicked()">area 2</DIV>
</Body>
Mozilla 系列浏览器支持这个 event.target所以自己可以做个判断，定一个函数
function clicked(e){
e = window.event || e; e = e.srcElement || e.target;
alert(e.id);
}
</script>
<DIV id="001" onclick="clicked(event)">area 1</DIV>