function popup(url, wnd_name, width, height, scrollbars)
{
   var stScrollBar = (scrollbars ? 'yes' : 'no');
   wnd = window.open(url, wnd_name, 'width='+width+', height='+height+', status=yes, menubar=no, resizable=yes, scrollbars='+stScrollBar+', left='+String((screen.width-width)/2)+', top='+String((screen.height-height)/2));
   if (wnd.focus) wnd.focus();
}