var NN  = document.layers;
var IE  = document.all;
var MAC = (navigator.appVersion.indexOf("Mac") != -1);

url="/css/";
if (MAC)
{ if (IE) cstyle="mac_ie.css";
  if (NN) cstyle="mac_ns.css";
}
else
{ if (IE) cstyle="pc_ie.css";
  if (NN) cstyle="pc_ns.css";
}	
document.write('<LINK REL=stylesheet TYPE="text/css" HREF="'+url+cstyle+'">');