JS to determine the user browser type code

<script type= "Text/javascript" >
var useragent = Navigator.userAgent.toLowerCase ();
var Is_opera = useragent.indexof (' opera ')!=-1 && opera.version ();
var Is_moz = (Navigator.product = = ' Gecko ') && useragent.substr (Useragent.indexof (' Firefox ') + 8, 3);
var Is_ie = (useragent.indexof (' MSIE ')!=-1 &&!is_opera) && useragent.substr (' Useragent.indexof ' ) + 5, 3);
function $$ (obj) {return document.getElementById (obj);}
function Getcookieval (offset) {var endstr = document.cookie.indexOf (";", offset); if (endstr = = 1) {endstr = document.co Okie.length;} Return unescape (document.cookie.substring (offset, endstr)); }
function GetCookie (name) {var arg = name + ' = '; var alen = arg.length; var Clen = Document.cookie.length;var i = 0;while (I < Clen) {var J = i + Alen; if (Document.cookie.substring (i, j) = arg) {return getcookieval (j);} i = Document.cookie.indexOf ("" , i) + 1; if (i = = 0) break; }return "";}
function Setcookie (name, value, expires, path, domain, secure) {Document.cookie = name + "=" + Escape (value) + ((expires)? "; Expires= "+ Expires:" ") + ((path)?"; Path= "+ Path:" "+ (domain)?"; domain= "+ domain:" ") + ((secure)?"; Secure ":" ");}
</script>