var myWindow;
function popup(url,width,height) {
    var left = parseInt((screen.availWidth/2) - (width/2));
    var top = parseInt((screen.availHeight/2) - (height/2));
    var windowFeatures = "width=" + width + ",height=" + height + 
        ",status,scrollbars, left=" + left + ",top=" + top + 
        "screenX=" + left + ",screenY=" + top;
    myWindow = window.open(url, "subWind", windowFeatures);
}