// browser
var ns = (navigator.userAgent.indexOf("Gecko") > 0) ? 1 : 0;
// platform
var mac = (navigator.userAgent.indexOf("Mac") > 0) ? 1 : 0;

if(mac==0) {
	document.write ('<link rel="stylesheet" type="text/css" href="css/pc.css">');
} else {
	document.write ('<link rel="stylesheet" type="text/css" href="css/mac.css">');
}