Detectar navegador con jQuery

Si se desea detectar navegador con jQuery, pdemos usar la siguiente script.

/*
* jQuery Browser Detect
*/

//Script para comprobar rutas de ficheros fisicos.
function file_exists (url) {
    var req = this.window.ActiveXObject ? new ActiveXObject("Microsoft.XMLHTTP") : new XMLHttpRequest();
    if (!req) {
        throw new Error('XMLHttpRequest not supported');
    }

    req.open('HEAD', url, false);
    req.send(null);
    if (req.status == 200){
        return true;
    }
    return false;
}

//Especificamos a jQuery los navegadores Util para diferenciar Safari de Chrome).
var userAgent = navigator.userAgent.toLowerCase();
jQuery.browser = {
    version: (userAgent.match( /.+(?:rv|it|ra|ie|me)[\/: ]([\d.]+)/ ) || [])[1],
    chrome: /chrome/.test( userAgent ),
    safari: /webkit/.test( userAgent ) && !/chrome/.test( userAgent ),
    opera: /opera/.test( userAgent ),
    msie: /msie/.test( userAgent ) && !/opera/.test( userAgent ),
    mozilla: /mozilla/.test( userAgent ) && !/(compatible|webkit)/.test( userAgent )
};



//Ejecutamos las condiciones si el fichero existe o no.
jQuery(document).ready(function($){
    var WMB_URL_CSS = '/sites/all/themes/wmb/css/browser/';  
    jQuery.each(jQuery.browser, function(i, val) {            
        if(file_exists(WMB_URL_CSS + "ie9.css") ){
            if(i=="msie" && jQuery.browser.version.substr(0,3)=="9.0"){
                $('head').append('<link rel="stylesheet" href="'+WMB_URL_CSS+'ie9.css" type="text/css" />');
            }
        }

        if(file_exists(WMB_URL_CSS + "ie8.css") ){
            if(i=="msie" && jQuery.browser.version.substr(0,3)=="8.0"){
                $('head').append('<link rel="stylesheet" href="'+WMB_URL_CSS+'ie8.css" type="text/css" />');
            }
        }

        if (file_exists(WMB_URL_CSS + "ie7.css")){
            if(i=="msie" && jQuery.browser.version.substr(0,3)=="7.0"){
                $('head').append('<link rel="stylesheet" href="'+WMB_URL_CSS+'ie7.css" type="text/css" />');
            }
        }

        if (file_exists(WMB_URL_CSS + "ie6.css")){
            if(i=="msie" && jQuery.browser.version.substr(0,3)=="6.0"){
                $('head').append('<link rel="stylesheet" href="'+WMB_URL_CSS+'ie6.css" type="text/css" />');
            }
        }

        if (file_exists(WMB_URL_CSS + "mozilla.css")){
            if($.browser.mozilla){                
                $('head').append('<link rel="stylesheet" href="'+WMB_URL_CSS+'mozilla.css" type="text/css" />');
            }
        }

        if (file_exists(WMB_URL_CSS + "opera.css")){
            if($.browser.opera){
                $('head').append('<link rel="stylesheet" href="'+WMB_URL_CSS+'opera.css" type="text/css" />');
            }
        }           

        if (file_exists(WMB_URL_CSS + "safari.css")){
            if($.browser.safari){                    
                $('head').append('<link rel="stylesheet" href="'+WMB_URL_CSS+'safari.css" type="text/css" />');
            }
        }

        if (file_exists(WMB_URL_CSS + "chrome.css")){
            if($.browser.chrome){                
                $('head').append('<link rel="stylesheet" href="'+WMB_URL_CSS+'chrome.css" type="text/css" />');
            }
        }
    });
});