怎么使弹出窗口居中显示

function selectProductFunction(height,width){
window.open ('selectProductPage.action', '选择产品', 'height='+height+', width='+width+',top='+(screen.height-height)/2+',left='+(screen.width-width)/2+' ,toolbar=no,menubar=no, scrollbars=no, resizable=no,location=n o, status=no'); 
}