var agt=navigator.userAgent.toLowerCase();
    var is_mac = (agt.indexOf("mac")!=-1);
 
    if (is_mac) {
        document.writeln('<style>');
        document.writeln('body, td, td p {font-size: 12pt}');
        document.writeln('p a {font-size: 13pt}');
        document.writeln('.header, .footer {font-size: 11pt}');
        document.writeln('<\/style>');
    }