css 文字位置的有关问题纠结

///这里是css
#id_top_div_mid {
    background-color: #D6D6D6;
    background-image: url(./img/top_barbackground_mid.jpg);
    background-repeat: repeat;
    width:644px;
    height:162px;
    float : left;
}

#id_top_div_name {
    background-repeat: norepeat;
    width:643px;
    height:130px;
    text-align : center;

}

h1 {
    font-size: 50px;
    font-style: normal;
    color: #FFAF09;
}

#id_top_div_menu {
    background-repeat: norepeat;
    width:643px;
    height:30px;
    text-align : center;

}

#id_top_menu{
    float: left;
    list-style: none outside none ;
    font-family:Verdana, Geneva, sans-serif;
    }
li{
        float: left;
        width: 80px;
        color: #FFAF09;
}    

/////下面是HTML

 <div class="c_top_div_mid" id="id_top_div_mid">
        <div class="c_top_div_name" id="id_top_div_name">
          <h1 id="main_title">这是公司的名称</h1>
      </div>
        <div class="c_top_div_menu" id="id_top_div_menu">
      <ul type="disc" class="c_top_menu" id="id_top_menu" title="首页,金麒麟KTV,大厅">
      <li><a href="" class="link"><span>网站首页</span></a></li>
      <li><a href="" class="link"><span>产品介绍</span></a></li>
      </ul>
      </div>

  </div>