HTML

<div class="menu">
    <ul>
      <li class="active"><a href="index.html">HOME</a></li>
      <li class="active"><a href="#">COMPANY</a></li>
      <li class="active"><a href="#">SOLUTIONS</a></li>
      <li class="active"><a href="#">SERVICES</a></li>
      <li class="active"><a href="#">NEWS & EVENTS</a></li>
      <li class="active"><a href="#">BLOGS</a></li>
      <li class="active"><a href="#">CONTACTS</a></li>
    </ul>
  </div>

CSS

.header .menu ul { margin:33px 10px 0 0; padding:0; float:right; width:auto; height:12px; list-style:none;}
.header .menu ul li { margin:0 4px; float:left;}

它无法识别高度特征.为什么？如何设置菜单项的高度？