title: How to make CSS Dropdown menu slidedown
body: <p>I created a CSS menu with dropdown and I hide the sub menu and display it when you hover over the menu item and I was wondering if it is possible with CSS with some type of CSS transition to make it instead slide down. You cake take a look at a mock up of the menu here. </p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>#main-nav {
    position: relative;
  }
  
  #main-nav&gt;ul&gt;li {
    width: 12.5%;
    float: left;
    text-align: center;
    line-height: .9em;
    font-weight: bold;
    background: #ccc;
  }
  
  #main-nav&gt;ul&gt;li&gt;a {
    display: block;
    color: #333;
    line-height: 12px;
    font-size: 14px;
    padding: 22px 0;
    text-decoration: none;
  }
  
  .nav-dropdown {
    margin: -5px auto;
    position: absolute;
    left: -999em;
    /* Hides the drop down */
    text-align: left;
    padding: 0;
    border-top: 0;
    width: 500px;
    background: #333;
    color: #f2f2f2;
    border-bottom: 10px solid #25272a;
    -webkit-border-bottom-right-radius: 5px;
    -webkit-border-bottom-left-radius: 5px;
    -moz-border-radius-bottomright: 5px;
    -moz-border-radius-bottomleft: 5px;
    border-bottom-right-radius: 5px;
    border-bottom-left-radius: 5px;
  }
  
  #main-nav li:hover .nav-dropdown {
    left: 0;
    top: auto;
    z-index: 11;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div id="main-nav"&gt;
    &lt;ul&gt;
      &lt;li&gt;&lt;a href="#"&gt;Item 1&lt;/a&gt;&lt;/li&gt;
      &lt;li&gt;&lt;a href="#"&gt;Item 2&lt;/a&gt;&lt;/li&gt;
      &lt;li&gt;&lt;a href="#"&gt;Item 3&lt;/a&gt;
        &lt;!-- Start Blog Drop Down--&gt;
        &lt;div class="nav-dropdown"&gt;
          &lt;p&gt;have this item slide down from CSS&lt;/p&gt;
        &lt;/div&gt;
        &lt;!-- /.nav-dropdown --&gt;
      &lt;/li&gt;
    &lt;/ul&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>