function openCenteredPopup(pageURL, w, h, showScrollBars) {
    var left = (screen.width / 2) - (w / 2);
    var top = (screen.height / 2) - (h / 2);
    var scrollbars = (showScrollBars == true ? 'yes' : 'no');
    var targetWin = window.open(pageURL, 'centeredPopupWindow', 'width=' + w + ', height=' + h + ', top=' + top + ', left=' + left + ', scrollbars=' + scrollbars);
}