function show_promo(content) {
    if(promo_window_handle == null) {
        promo_window_handle = window.open('','_csbr_promo','height=600px,width=620px,menubar=0,status=0,scrollbars=1,resizable=1');
        promo_window_handle.document.open();
    }
    promo_window_handle.document.write(content);
    promo_window_handle.document.close();
    promo_window_handle.focus();
}