var obj = newWindow;
obj.style.left = (document.body.clientWidth - obj.width)/2;
obj.style.top = (document.body.clientHeight - obj.height)/2;
obj.style.left = (document.body.clientWidth - obj.width)/2;
obj.style.top = (document.body.clientHeight - obj.height)/2;
screen.width,screen.height可以取得屏幕高宽