Div被另一个覆盖，z-index不起作用

Question

我使用Easy-UI布局，蓝色部分是＆＃34; north＆＃34;布局显示导航，向下是布局部分＆＃34; center＆＃34;。

但是下拉div被＆＃34; center＆＃34;覆盖。鼠标移动时的布局面板。

我将z-index设置为pulldown div，但它不起作用。我该如何解决？

＆＃13;

＆＃13;

.hd-main .has-pulldown {
  cursor: pointer;
  position: relative;
  *z-index: 10000
}
.hd-main .pulldown {
  position: absolute;
  cursor: default;
  display: none;
  top: 30px;
  left: 0
}
.hd-main .pulldown .arrow {
  *margin-bottom: -1px;
  _margin-bottom: 0;
  height: 0;
  width: 0;
  font-size: 0;
  line-height: 0;
  border-width: 7px;
  border-style: solid;
  border-color: transparent transparent #F6F6F9 transparent;
  _filter: chroma(color=tomato);
  _border-color: tomato tomato #F6F6F9 tomato;
  position: relative;
  display: block;
  left: 20px;
  z-index: 2
}
.hd-main .pulldown .content {
  background: #F6F6F9;
  color: #333;
  text-align: left;
  border-radius: 3px;
  border: rgb(175, 175, 175) 1px solid;
  border-width: 0 1px 1px 1px;
  box-shadow: 0 2px 4px rgba(0, 0, 0, .2);
  position: relative;
  z-index: 1
}
.hd-main .pulldown-canvas {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  opacity: 0;
  filter: alpha(opacity=0)
}
.hd-main .navs .def-nav,
.hd-main .navs .pulldown-nav,
.hd-main .navs .separate {
  display: block;
  float: left;
  height: 48px;
  font: 18px/30px"Microsoft YaHei", "Microsoft JhengHei";
  color: #d8d8d8;
  text-align: center;
  width: 90px;
  line-height: 48px
}
.hd-main .navs .pulldown-nav {
  position: relative
}
.hd-main .navs .pulldown-nav em {
  position: absolute;
  display: block;
  left: 69px;
  top: 18px;
  height: 12px;
  width: 12px;
  font-size: 0;
  background-position: -89px -45px
}
.hd-main .navs .pulldown-nav:hover .f-icon,
.hd-main .navs .pulldown-nav:active .f-icon {
  position: absolute;
  display: block;
  right: 11px;
  top: 18px;
  height: 12px;
  width: 12px;
  font-size: 0;
  background-position: -89px -55px
}

＆＃13;

<ul>
  <li class="info-i user-name has-pulldown">
    <em class="f-icon pull-arrow"></em>
    <span class="name top-username">David</span>
    <div class="pulldown user-info">
      <em class="arrow"></em>
      <div class="content">
        <span class="li"><a href="">aa</a></span>
        <span class="li"><a href="">bb</a></span>
        <span class="li"><a href="">cc</a></span>
        <span class="li"><a href="">dd</a></span>
        <span class="separate-li no-height"></span>
        <span class="li"><a href="javascript:;" id="signout">Log Out</a></span>
      </div>
    </div>
  </li>
</ul>

＆＃13;

＆＃13;

＆＃13;