//OSの種類判定
function getOSType(){
var uAgent = navigator.userAgent.toUpperCase();
if (uAgent.indexOf("MAC") >= 0) return "mac";
if (uAgent.indexOf("WIN") >= 0) return "Win";
return "";
}

cssfile ="css/mac.css";
os = getOSType();

if(os == "mac"){
link = document.createElement("link");
link.setAttribute("rel","stylesheet");
link.setAttribute("href",cssfile);
link.setAttribute("type","text/css");

head = document.getElementsByTagName('head').item(0);
head.appendChild(link);
}