yourBrowser = navigator.appName;
yourAppVersion = parseInt(navigator.appVersion);
isIE = "Microsoft Internet Explorer";
isNS = "Netscape";
if (navigator.appVersion.indexOf("Macintosh") != -1) {
	isMac = true;
} else {
	isMac = false;
}
if (document.getElementById) {
	// IE 5 ^ & NN 6 ^
	if(yourBrowser == isNS){
		document.write('<link rel="stylesheet" type="text/css" href="/css/styles.css">');
	} else {
		document.write('<link rel="stylesheet" type="text/css" href="/css/styles.css">');
	}
} else {	
	if (yourBrowser == isNS && isMac == false) {
		// NN 4 ^ on PC
		if (yourAppVersion > 3) {
			document.write('<link rel="stylesheet" type="text/css" href="/css/styles_nn4.css">');
		}
	} else if (yourBrowser == isIE && isMac == true) {
		// IE on Mac
		document.write('<link rel="stylesheet" type="text/css" href="/css/styles.css">');
	} else if (yourBrowser == isNS && isMac == true) {
		// NN on Mac
		document.write('<link rel="stylesheet" type="text/css" href="/css/styles.css">');
	} else {
		// Anything Else
		document.write('<link rel="stylesheet" type="text/css" href="/css/styles.css">');
	}
}