var agt=navigator.userAgent.toLowerCase();
var os=navigator.platform;
if (parseInt(navigator.appVersion)>=4 && (agt.indexOf('msie') != -1 || agt.indexOf('netscape6')!=-1)) 
{
   if (os.indexOf("Mac") != -1){
    document.write('<link href="css/mac_ie.css" rel=stylesheet type="text/css">');
   }else{
    document.write('<link href="css/pc_ie.css" rel=stylesheet type="text/css">');
   }
}
else//ntsc ausser netsc6 
{
if (os.indexOf("Mac") != -1){
     document.write('<link href="css/mac_ntsc.css" rel=stylesheet type="text/css">');
  }else{
   document.write('<link href="css/pc_ntsc.css" rel=stylesheet type="text/css">');
  }
}