var isMac = (navigator.userAgent.toLowerCase().indexOf("mac") != -1);
var isIE = (document.all);
var isNav = (document.layers);

if (isMac) {
	document.write('<link rel="stylesheet" href="mac.css">');
} else {
	if (isNav) {
		document.write('<link rel="stylesheet" href="win2.css">');
	} else {
		document.write('<link rel="stylesheet" href="win1.css">');
	}
}