function showNew()
{
var width=200;
var height=200;
var y=(window.screen.availHeight-200);
var x=(window.screen.availWidth-200);
var mywindow=window.open("","_blank","height="+height+",width="+width);
mywindow.moveTo(x/2,y/2);
}
</script>
<input type="button" value="点击" onclick="showNew()">
window.open窗口显示在屏幕中央
原文：http://www.cnblogs.com/feng12345/p/5324389.html
