如何让window.open弹出窗口总在最前！

下面的代码可以模仿模态窗口
<script>
var WinWidth = 400;
var WinHeight = 300; var win = window.open("about:blank")
win.moveTo(Math.round((screen.Width - WinWidth)/2),Math.round((screen.Height - WinHeight)/2) + 20)
win.location = "http://lucky.myrice.com"
win.document.body.style.overflow = "hidden"function focusWin()
{
if(win && win.open && !win.closed) 
win.focus();
}
window.onfocus = focusWin;
</script><body onfocus="focusWin();" onmousemove = "focusWin();" onkeydown = "focusWin();">
模仿 window.showModalDialog() 的窗口！！