var agt=navigator.userAgent.toLowerCase();
var isMajor=parseInt(navigator.appVersion);
var isMinor=parseFloat(navigator.appVersion);
var isNav=((agt.indexOf('mozilla')!=-1) && (agt.indexOf('spoofer')==-1)  &&
(agt.indexOf('compatible') == -1) &&
(agt.indexOf('opera') == -1) && (agt.indexOf('webtv') ==-1));
var isNav4=(isNav && (isMajor < 5));
var isNav6=(isNav && (isMajor >=5));
var isIe=(agt.indexOf("msie") != -1);
var isIe4=(isIe && (isMajor >=4));


if (isNav4) {
	document.write('<link rel="stylesheet" type="text/css" href="http://www.keatingweb.com/html/css/nsStyles.css">');
}
if (isIe){
	document.write('<link rel="stylesheet" type="text/css" href="http://www.keatingweb.com/html/css/ieStyles.css">');
}
if (isNav6) {
	document.write('<link rel="stylesheet" type="text/css" href="http://www.keatingweb.com/html/css/ns6Styles.css">');
}

<!--
function reloadPage(init) {  //reloads the window if Nav4 resized
  if (init==true) with (navigator) {if
((appName=="Netscape")&&(parseInt(appVersion)==4)) {
    document.pgW=innerWidth; document.pgH=innerHeight;
onresize=reloadPage; }}
  else if (innerWidth!=document.pgW || innerHeight!=document.pgH)
location.reload();
}
reloadPage(true);
// -->