function popup(url, width, height, name)
{
    var features = 'width=' + width + ',height=' + height + ',left=' + (screen.width - width)/2 + ',top=' + (screen.height - height)/2 + ',scrollbars';
    var popupWindow = window.open(url, name, features);
    if(popupWindow.focus) {popupWindow.focus();}
}