弹出窗口居中显示

<script>
//弹出窗口居中显示
functionopenWin(){
varhdc=window.open("product1_add.html","_blank",'height=200px,width=400px,status=yes,toolbar=no,menubar=no,location=no');
width=screen.width;
height=screen.height;
hdc.moveTo((width-400)/2,(height-200)/2);
}
</script>