var ns4 = (document.layers)? true:false;
var ns6 = (document.getElementById)? true:false;
var ie = (document.all)? true:false;

if (ns4) {
	document.write('<link rel="StyleSheet" href="css/ns4.css" type="text/css">')
}

else if (ie) {
	document.write('<link rel="StyleSheet" href="css/explorer.css" type="text/css">')	
}

else if (ns6) {
	document.write('<link rel="StyleSheet" href="css/firefox.css" type="text/css">')
}

else {
	alert("Your browser does not support css! Try a new version.");
}