高手：win xp sp2 IE6 : javascript 认不到window.open()打开的窗体。怎么办？

<html>
<head>
<script type="text/javascript">
<!--为什么有些IE可以实现，有些IE不能实现Close. 同样是IE6. 也就是说读不到open的child， 怎么解决能实现？-->
function opens()
{
var win= window.open("","child","top=400,left=100,width=200,height=200,toolbar=0,status=1,menubar=0,scrollbars=0,resizable=1");
win.focus();//win.close();
}

function closes()
{
var win= window.open("","child","top=400,left=100,width=200,height=200,toolbar=0,status=1,menubar=0,scrollbars=0,resizable=1");
win.focus();win.close();
}

</script>
</head>
<body>
<div id="divDemo">open and close ie window</div>

<input type="button" value="Open" onclick="opens();" />

<input type="button" value="Close" onclick="closes();" />

<br/>
<br/>

open , can not close.

</body>
</html>