var Zeile, CSSFile;

      if
      ((navigator.appVersion.indexOf("Mac")!=-1)
      &&(parseInt(navigator.appVersion.charAt(0))>=4))
      {
      CSSFile="form_mac.css";
      }

      if
      ((navigator.appVersion.indexOf("Win")!=-1)
       &&(parseInt(navigator.appVersion.charAt(0))>=4))
      {
      CSSFile="form.css";
      }

      Zeile="<LINK REL=\"STYLESHEET\" HREF=\""+CSSFile+"\" TYPE=\"text/css\">";
      document.write(Zeile);