var ua = navigator.userAgent;
if (ua.indexOf('Mozilla') != -1 && ua.indexOf('Macintosh') != -1 && ua.indexOf('Safari') == -1) {
  // the browser claims to be:
  //   Mozilla based
  //   running on a Macintosh
  //   and it is not Safari
  // alert('Welcome to Firefox on the Mac');
  document.write('<'+'link rel="stylesheet" href="/css/ffm_fix.css"'+'>');
}