function popup(url, w, h, scroll) {
    //Source: http://www.boutell.com/newfaq/creating/windowcenter.html
    var name = '_blank';

    // Fudge factors for window decoration space.
    // In my tests these work well on all platforms & browsers.
    w += 32;
    h += 96;
    wleft = (screen.width - w) / 2;
    wtop = (screen.height - h) / 2;
    var win = window.open(url,
    name,
    'width=' + w + ', height=' + h + ', ' +
    'left=' + wleft + ', top=' + wtop + ', ' +
    'location=no, menubar=no, ' +
    'status=yes, toolbar=no, scrollbars=' + scroll + ', resizable=no');

    // Just in case width and height are ignored
    win.resizeTo(w, h);

    // Just in case left and top are ignored
    win.moveTo(wleft, wtop);
    win.focus();
}