Detecting browser versions and Operating Systems with jquery

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js"></script>
<script type="text/javascript" src="jquery.client.js"></script>
Download clients.js here

<script type="text/javascript">
$(function() {

//Firefox 3.6
var version=jQuery.browser.version;
if (jQuery.browser.mozilla) {   
    var verarray=version.split('.');
    if(verarray[0]=='1' && verarray[1]=='9')
    {
        /*var head= document.getElementsByTagName('head')[0];
        var addCSS= document.createElement('link');
        addCSS.href = 'css/CSIdentity.ff3.5.css';
        addCSS.rel = 'stylesheet';
        addCSS.type = 'text/css';
        head.appendChild(addCSS);*/
        $(".nav li:first-child").css({"padding":"10px"})
    }   
}   
//Mac Safari 5
var dos = $.client.os;
var dbv = $.client.browser=="Safari";
if(dos == "Mac" && dbv && (navigator.appVersion.indexOf('5.') != -1)){
    $(".nav li:first-child").css({"padding":"20px"})
}
//Mac Chrome
var dbvch = $.client.browser=="Chrome";
if(dos == "Mac" && dbvch){
    $(".nav li:first-child").css({"padding":"24px"})
}
//Mac Firefox 3.6
if(dos == "Mac" && jQuery.browser.mozilla){
    var verarray=version.split('.');
    if(verarray[0]=='1' && verarray[1]=='9')
    {       
        $(".nav li:first-child").css({"padding":"26px"});
    }   
}
//FF 4.0
if(dos == "Mac" && jQuery.browser.mozilla && version == "2.0"){
    $(".nav li:first-child").css({"padding":"28px"});       
}
//FF 5.0
if(dos == "Mac" && jQuery.browser.mozilla && version == "5.0.1"){
    $(".nav li:first-child").css({"padding":"30px"});
}

//Windows Vista FF
if(navigator.oscpu == "Windows NT 6.0" && jQuery.browser.mozilla && version == "2.0"){ 
    $(".nav li:first-child").css({"padding":"32px"});
}
if(navigator.oscpu == "Windows NT 6.0" && jQuery.browser.mozilla && version == "5.0.1"){ 
    $(".nav li:first-child").css({"padding":"8px"});   
}
if(navigator.oscpu == "Windows NT 6.0" && jQuery.browser.mozilla && version == "6.0.2"){ 
    $(".nav li:first-child").css({"padding":"6px"});   
}