我想创建一个文本居中的导航栏,但是我的 CSS 代码将超链接放置在 li 的上角,如图所示。

CSS:
#navigation {
    clear: both;
    margin: 0 auto 5px;
    margin-top: 0;
    height: 6%;
    padding: 0 5px;
    position: relative;
    z-index: 1;
}
#navigation  a {
    height: 10%;
    width: 50px;
    color: red;
    vertical-align: center;
    text-align: center;
    text-decoration: bold;
}
li {
    border-top: solid;
    border-right: solid;
    border-left: solid;
    border-bottom: none;
    padding-left: 1px;
    height: 51px;
    width: 18%;
    background-image: url('../images/tab-selected.png');
    background-repeat: repeat-x-y;
    border-color: #F0F0F0;
    display: inline-block;
    padding-left: 1px;
}
HTML:
<nav id="navigation">
  <ul>
    <li ><a href="overview.asp">overview</a></li>
    <li ><a href="overview.asp">overview</a></li>
 </ul>  
</nav>