title: CSS Drop down menu is hiding behind a div (already tried z-index)
body: <p>I´m trying to place a CSS sub-menu over a div, and I already tried using z-index, but it´s still not working. Here is the HTML code:</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
      &lt;head&gt;
          &lt;title&gt;Concurso&lt;/title&gt;
          &lt;link type="text/css" rel="stylesheet" href="styles.css"&gt;
      &lt;/head&gt;
      &lt;body&gt;
          &lt;div id="frame-superior"&gt;
              &lt;div id="menu"&gt;
              &lt;ul&gt;
                  &lt;li&gt;
                      &lt;a href="#"&gt;HOME&lt;/a&gt;
                  &lt;/li&gt;
                  &lt;li&gt;
                      &lt;a href="#"&gt;Receitas&lt;/a&gt;
                      &lt;ul&gt;
                          &lt;li&gt;&lt;a href="#"&gt;Receita 1&lt;/a&gt;&lt;li&gt;
                          &lt;li&gt;&lt;a href="#"&gt;Receita 2&lt;/a&gt;&lt;li&gt;
                          &lt;li&gt;&lt;a href="#"&gt;Receita 3&lt;/a&gt;&lt;li&gt;
                      &lt;/ul&gt;
                  &lt;/li&gt;
                  &lt;li&gt;
                      &lt;a href="#"&gt;O Concurso&lt;/a&gt;
                  &lt;/li&gt;
                  &lt;li&gt;
                      &lt;a href="#"&gt;Edi&amp;ccedil;&amp;otilde;es anteriores&lt;/a&gt;
                      &lt;ul&gt;
                          &lt;li&gt;&lt;a href="#"&gt;Edi&amp;ccedil;&amp;atilde;o 1&lt;/a&gt;&lt;li&gt;
                          &lt;li&gt;&lt;a href="#"&gt;Edi&amp;ccedil;&amp;atilde;o 2&lt;/a&gt;&lt;li&gt;
                          &lt;li&gt;&lt;a href="#"&gt;Edi&amp;ccedil;&amp;atilde;o 3&lt;/a&gt;&lt;li&gt;
                      &lt;/ul&gt;
                  &lt;/li&gt;
                  &lt;li&gt;
                      &lt;a href="#"&gt;Contato&lt;/a&gt;
                  &lt;/li&gt;
                &lt;/ul&gt;
              &lt;/div&gt;
          &lt;/div&gt;
          &lt;div id="frame-inferior"&gt;
              &lt;img id="but-inicial" src="but-inicial.jpg"/&gt;
          &lt;/div&gt;
      &lt;body/&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>And here is the CSS code:</p>
  
  <pre><code>/* Contain floats: h5bp.com/q */
  #menu &gt; ul:before, #menu &gt; ul:after {
      content: "";
      display: table;
  }
  
  #menu &gt; ul:after {
      clear: both;
  }
  
  #menu &gt; ul {
      *zoom: 1;
  }
  
  /* Level one */
  #menu &gt; ul &gt; li {
      float:left;
      position:relative;
      overflow:visible;
      width:30%;
      max-width:190px;
      list-style-type: none;
      font-size: 0.5em;
      z-index: 2;
  }
  #menu &gt; ul &gt; li &gt; a{
      padding:.5em 1em;
      position: relative;
      z-index: 2;
  }
  
  /* Level 2*/
  #menu &gt; ul &gt; li &gt; ul {
      background:#afeeee;
      border-radius: 0 5px 5px 5px;
      position:absolute;
      z-index: 2;
      padding:1em;
      width:200px; /*set to whatever you need*/
      display:none;
  }
  
  /* Segunda lista do level 2*/
  #menu &gt; ul &gt; li:nth-child(2) &gt; ul{
      margin-left:-50%;
      border-radius: 5px;
      list-style-type: none;
      position: absolute;
      z-index: 2;
  }
  
  /*Quarta lista do level 2*/
  #menu &gt; ul &gt; li:nth-child(4) &gt; ul{
      margin-left:-50%;
      border-radius: 5px;
      list-style-type: none;
      position: absolute;
      z-index: 2;
  }
  
  /* Última lista do level 2*/
  #menu &gt; ul &gt; li:last-child &gt; ul{
      right:0;
      border-radius: 5px 0 5px 5px;
      position: absolute;
      z-index: 2;
  }
  
  /* Hover level 1*/
  #menu &gt; ul &gt; li:hover {
      background: #afeeee;
      border-radius: 5px 5px 0 0;
      color:#fff;
  }
  
  #menu &gt; ul &gt; li:hover &gt; ul {
      display:block;
      position: absolute;
      z-index: 3;
  }
  
  #menu &gt; ul &gt; li:hover &gt; a,
  #menu &gt; ul &gt; li &gt; ul a{
      color:#fff;
  }
  
  #menu a {
      text-decoration:none;
      display:block;
  }
  body {
      margin: 0;
      padding: 0;
      border: 0;
      overflow: hidden;
      height: 100%; 
      max-height: 100%; 
      color: black;
  }
  #frame-superior {
      background-image: url(fundo-superior.jpg);
      background-repeat: no-repeat;
      background-size: cover;
      background-position: center center;
      font-size: 50px;
      position: absolute; 
      top: 0; 
      left: 0; 
      width: 100%; 
      height: 200px;
      overflow: hidden; /*Disable scrollbars. Set to "scroll" to enable*/
      z-index: 2;
  }
  #frame-inferior {
      /*background-image: url(buteco-inicial.jpg);
      background-repeat: no-repeat;
      background-size: cover;
      background-position: center center;*/
      font-size: 50px;
      position: absolute; 
      top: 200px; /*Colocar o mesmo valor da height do frame-superior*/
      left: 0;
      right: 0;
      bottom: 0;
      overflow: hidden; 
      z-index: 0;
  }
  #but-inicial {
      width: 100%;
      position: absolute;
      margin-top: -25%;
      z-index: 0;
  }
  </code></pre>
  
  <p>The sub-menus keep going behind the image (or behind the div frame-inferior).</p>