title: Why won't the z-index on my elements work?
body: <p>I have my code set up so I have the hero image at the bottom and the overlay on top with the text and button in overlay. I also have the navigation bar with a z-index but for some reason the button for my resume in overlay isn't working.</p>
  
  <p>HTML<br>
      </p>
  
  <pre><code>    &lt;div id="header"&gt;
          &lt;a href="index.html"&gt;&lt;div id="leftHeader"&gt;
          &lt;img src="assets/logo2.jpg" alt="Logo" style="width:65px;height:65px"&gt;
          &lt;h1&gt;Amanda Farrington&lt;/h1&gt;
      &lt;/div&gt;
          &lt;div id="nav"&gt;
  
        &lt;ul&gt;
          &lt;li&gt;&lt;a href="about.html"&gt;About&lt;/a&gt;&lt;/li&gt;
          &lt;li&gt;&lt;a href="#workJump"&gt;Work&lt;/a&gt;&lt;/li&gt;
          &lt;li&gt;&lt;a href="contact.html"&gt;Contact&lt;/a&gt;&lt;/li&gt;
          &lt;li&gt;&lt;a href="notes.html"&gt;Notes&lt;/a&gt;&lt;/li&gt;
        &lt;/ul&gt;
          &lt;/div&gt;
      &lt;/div&gt;
  
  
  
      &lt;div id="hero"&gt;
          &lt;div id="heroImage"&gt;
          &lt;img src="assets/trees.jpg" alt="trees" style="width:100%;height:10%"&gt;
          &lt;/div&gt;
  
          &lt;div id="overlay"&gt;
          &lt;h2&gt;Amanda Farrington&lt;/h2&gt;
          &lt;h3&gt;Graphic Artist | Web Designer&lt;/h3&gt;
      &lt;a href="assets/resume.pdf" class="down"&gt;View Resume&lt;/a&gt;                
  
  
          &lt;/div&gt;
      &lt;/div&gt;
  </code></pre>
  
  <p>CSS</p>
  
  <pre><code>#header {
    color: #D7DADB;
    font-family: 'Roboto', sans-serif;
    font-weight: 300;
    font-size : 15px;
    text-align: left;
    width: 100%;
    padding-left: 3em;
    position: relative;
    height: 15%;
    box-sizing: border-box;
    padding-top: 1em;
  
  }
  
  
  #header img
  {
      float: left;
      padding-left: 3em;
  }
  
  h1{
  width: 9em;
  float: left;
  padding-left: 0.5em;
  color: #45CCCC;
  padding-bottom: 1px;
  }
  
  #nav {
    width: 50%;
    margin:0;
    padding:0;
    text-align: right;
    color: red;
    font-size:20px;
    float: right;
    padding-right: 2em;
    z-index: 99;
  
  }
  
  #nav ul {
    padding: 1px;
  }
  
  #nav li {
    display: inline;
    padding: 38px;
  }
  
  #nav li a {
    color: #2C3E50;
    text-decoration: none;
  }
  
  #nav li a:hover {
    color: #45CCCC;
  }
  
  /*----------hero image styles-------------*/
  #hero{
      padding-top: 25em;
      width: 100%;
      height: 30em;
      position: relative;
      z-index: -1;
  }
  
  #heroImage
  {
      top: 9%;
      width: 100%;
      z-index: 1;
      position: absolute;
  
  }
  
  #overlay{
      width: 34em;
      top: -15%;
      margin-left: 30%;
      z-index: 2;
      position: relative;
      clear: left;
  
  
  }
  
  h2{
      width: 100%;
      position: relative;
      font-family: 'Roboto', sans-serif;
      font-weight: 300;
      font-size: 60px;
      float: center;
      color: white;
      opacity: 1.0;
      text-shadow: 2px 2px 3px #000000;
      text-align: center;
  }
  
  h3{
      width: 100%;
      position: relative;
      font-family: 'Roboto', sans-serif;
      font-weight: 300;
      font-size: 30px;
      color: #e5e5e5;
      opacity: 1.0;
      text-shadow: 2px 3px 2px #000000;
      text-align: center;
  
  }
  
  a.down{
      z-index: 100;
      font-family: 'Roboto', sans-serif;
      font-weight: 400;
      text-decoration: none;
      color: #181b1e;
      background: #45CCCC;
      position: relative;
      padding: 0.6em 0.2em;
      font-size: 1.2em;
      -webkit-border-radius: 6px;
      width: 30%;
      position: relative;
      display: block;
      margin-left: auto;
      margin-right: auto;
      text-align: center;
  
  }
  
  a.down:hover{
      text-decoration: underline;
      color: white;
  
  }
  </code></pre>