firefox与ie的在html中放onclick="func()"时的func的this的区别

<script>
function func(e) {
alert(this);
}
</script>
<a href="#333" target="_self" onclick="func();">ddd</a>
<a onclick="func();">ddd</a>
<button onclick="func();">ddd</button>
<img alt="dkddkdk" src="http://tx.bdimg.com/sys/portraitn/item/d7dec3cec2b6dcb7b6f9a420.jpg" onclick="func();"/>
---------在ie中总是点击的对象-------
在firefox中却是window