function openWindow(url, w, h, num){
 window.open(url, num, 'width='+ w +', height=' + h + ', left='+(screen.width-w)/2+', top='+(screen.height-h)/2+', resizable=no, scrollbars=no, toolbars=no, location=no, directories=no, status=no, menubar=no, copyhistory=no');
}