Problém s drop-down menu

<ul class="float">
      <li><a href="#" >polozka 1</a></li>
      <li><a href="#">polozka 2</a>
          <ul>
              <li><a href="#">subpolozka 1</a></li>
              <li><a href="#">subpolozka 2</a></li>
              <li><a href="#">subpolozka 3</a></li>
          </ul>
      </li>
      <li><a href="#">polozka 3</a></li>
    </ul>

#head ul  {list-style: none;}
#head ul li {float: left; display: block;}
#head ul li ul li {float: none; text-align: left; padding: 8px 12px; background: #0070b2;}
#head ul li ul li a {text-decoration: none; color: white; font-weight: bold;}
#head ul li ul li a:hover {text-decoration: underline;}
ul.float  {float: left; list-style-type: none; display: block;}
ul.float li ul {display: none; position: absolute;}
ul.float li:hover ul {display: block; position: absolute; z-index: 1000; top: 100px;}