function detectMacXFF() {
  var userAgent = navigator.userAgent.toLowerCase();
  if (userAgent.indexOf('mac') != -1 && userAgent.indexOf('firefox')!=-1) {
    return true;
  }
}

var d = detectMacXFF();
  if (d) {
	//osx ff css opacity + flash wmode transparent doesn't work so transparent png is needed in background
	document.writeln("<style type=\"text/css\" media=\"screen\">");
	document.writeln("<!--");
	document.writeln("#nav-bar ul li ul { background:url(fileadmin/templates/gfx/fff-60.png) repeat ! important; }");
	document.writeln("-->");
	document.writeln("</style>");
  } else {
	//css opacity for all other browsers
	document.writeln("<style type=\"text/css\" media=\"screen\">");
	document.writeln("<!--");
	document.writeln("#nav-bar ul li ul {");
	document.writeln("background:#fff;");
	document.writeln("filter:alpha(opacity=70);");
	document.writeln("opacity:0.7;");
	document.writeln("-moz-opacity:0.7;");
	document.writeln("}");
	document.writeln("-->");
	document.writeln("</style>");
  }