javascript封锁IE不弹出对话框

<script type="text/javascript">
function closeWindow(){
	var ua = navigator.userAgent.toLowerCase(); 
	if(ua.indexOf('MSIE 5.0')!=-1||ua.indexOf('MSIE 6.0')!=-1){ 
		window.opener=null;
 		window.close();
	}else {
		window.opener=null;
		window.open('','_top');
		window.close();
	}
}
</script>

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