麻烦老师看下代码，导航居中显示有点问题，谢谢

相关代码：html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>慕云游商城 - 机票、酒店、旅游攻略</title>
    <meta name="Keywords" content="机票，酒店，旅游攻略，签证，出国，自由行">
    <meta name="Description" content="慕云游商城有10多年旅游行业经验，为您提供全方位旅游服务">
    <link rel="stylesheet" href="css/rest.css">
    <link rel="stylesheet" href="css/base.css">
    <link rel="stylesheet" href="css/css.css">

</head>
<body>
    <!-- 网页顶部 -->
    <header class="site-head">
        <div class="topbar">
            <div class="center-wrap">
                <nav class="shortcut-links">
                    <ul>
                        <li>
                            <a href="">目的地</a>
                        </li>

                        <li>
                            <a href="">锦囊</a>
                        </li>

                        <li class="have-menu">
                            <a href="">社区</a>
                            <em class="arrow">
                                <b></b>
                                <i></i>
                            </em>
                        </li>

                        <li>
                            <a href="">行程助手</a>
                        </li>

                        <li class="have-menu">
                            <a href="">商城</a>
                            <em class="arrow">
                                <b></b>
                                <i></i>
                            </em>
                        </li>

                        <li class="have-menu">
                            <a href="">酒店.民宿</a>
                            <em class="arrow">
                                <b></b>
                                <i></i>
                            </em>
                        </li>


                        <li>
                            <a href="">特价酒店</a>
                        </li>


                    </ul>
                </nav>
                </div>
            </div>
    </header>
</body>
</html>

相关代码：css.css

.site-head{
    height: 150px;


}

.site-head .topbar{
    height: 32px;
    background-color:#2A2A2A;
    line-height: 32px;





}

.site-head .topbar a{
    color: white;
}
.site-head .topbar .shortcut-links{
    float: left;
}



.site-head .topbar .shortcut-links ul li{
    float:left;
    margin-right: 18px;
    font-size: 14px;
}

.site-head .topbar .shortcut-links ul li.have-menu{
    padding-right:12px;
    position: relative;


}

.site-head .topbar .shortcut-links ul li.have-menu .arrow{
    position: absolute;
    right:0;
    top: 50%;
    margin-top: -6px;
    width: 12px;
    height: 12px;
    transition: transform .2s ease 0s;

}

.site-head .topbar .shortcut-links ul li.have-menu:hover .arrow{
    transform: rotate(180deg);
}



.site-head .topbar .shortcut-links ul li.have-menu .arrow b{
    position: absolute;
    top: 2px;
    left: 3px;
    width: 6px;
    height: 6px;
    background-color:white;
    transform: rotate(45deg);
}

.site-head .topbar .shortcut-links ul li.have-menu .arrow i{
    position: absolute;
    left: 3px;
    top:0.5px;
    width: 6px;
    height:6px;
    background-color:#2A2A2A;
    transform: rotate(45deg);
}

相关代码：base.css

@font-face{
    font-family: "PIngFangSCRegular";
    src:url(../fonts/PingFangSCRegular.ttf) format('truetype')
}

body{
    font-family: "PIngFangSCRegular";
}



 .center-wrap{
    width: 1152px;
    margin: 0 auto;
}

.clearfix{
    overflow: hidden;
}

.clearfix::after{
    content: '';
    display: block;
    clear: both;
    overflow: hidden;
}

.db{
    display: block;
}

.dib{
    display: inline-block;
}

.tac{
    text-align: center;
}

相关代码：rest.css

/*
YUI 3.18.1 (build f7e7bcb)
Copyright 2014 Yahoo! Inc. All rights reserved.
Licensed under the BSD License.
http://yuilibrary.com/license/
*/

html{color:#000;background:#FFF}body,div,dl,dt,dd,ul,ol,li,h1,h2,h3,h4,h5,h6,pre,code,form,fieldset,legend,input,textarea,p,blockquote,th,td{margin:0;padding:0}table{border-collapse:collapse;border-spacing:0}fieldset,img{border:0}address,caption,cite,code,dfn,em,strong,th,var{font-style:normal;font-weight:normal}ol,ul{list-style:none}caption,th{text-align:left}h1,h2,h3,h4,h5,h6{font-size:100%;font-weight:normal}q:before,q:after{content:''}abbr,acronym{border:0;font-variant:normal}sup{vertical-align:text-top}sub{vertical-align:text-bottom}input,textarea,select{font-family:inherit;font-size:inherit;font-weight:inherit;*font-size:100%}legend{color:#000}#yui3-css-stamp.cssreset{display:none}a{text-decoration: none;}