function tell_a_friend(URL) 
{
    day = new Date();
    id = day.getTime();
    var left = (screen.width - 600) / 2;
    var top = (screen.height - 550) / 2;
    eval("page" + id + " = window.open(URL, '" + id + "', 'toolbar=0,scrollbars=1,location=0,statusbar=0,menubar=0,resizable=0,width=600,height=500,left='+left+',top='+top);");
}