title: HTML drop down menu make <div> height longer
body: <p>My div height in HTML will become longer when drop down menu expand. I am new to CSS. The dropdown menu name is <code>portfolio</code>. When I move cursor into it, my HTML page become longer. </p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>* {
    padding: 0;
    margin: 0;
  }
  body {
    font-family: 'Droid Serif', serif;
    font-size: 12px;
    color: #9b9e9a;
    background: #e1ece7;
  }
  img {
    border: none;
  }
  h1 {
    font-size: 18px;
    color: #d13f31;
    font-family: 'Oswald', sans-serif;
    font-weight: normal;
    text-transform: none;
  }
  h2 {
    font-size: 14px;
    color: #1f7872;
    font-family: 'Droid Serif', serif;
    font-weight: normal;
  }
  P {
    line-height: 20px;
  }
  a {
    text-decoration: none;
    color: #1f7872;
  }
  a:hover {
    color: #d13f31;
  }
  .mar-top30 {
    margin-top: 30px;
  }
  .mar-top20 {
    margin-top: 20px;
  }
  .mar-right30 {
    margin-right: 30px;
  }
  .mar-bottom20 {
    margin-bottom: 20px;
  }
  .float-left {
    float: left;
  }
  .float-right {
    float: right;
  }
  .clearing {
    clear: both;
  }
  .panel {
    background: #ffffff;
  }
  .title {} .content {} .button a {
    text-decoration: none;
    display: block;
    width: 70px;
    height: 30px;
    background: #1f7872;
    color: #ffffff;
    font-family: 'Oswald', sans-serif;
    line-height: 30px;
    text-align: center;
    text-transform: uppercase;
  }
  .button a:hover {
    background: #d13f31;
  }
  .page {
    width: 960px;
    margin: 0 auto;
    overflow: hidden;
  }
  .menu-wrap {
    overflow: hidden;
    background: #1a202c;
  }
  .menu {
    margin: 0 auto;
    width: 960px;
    height: 85px;
    margin-top: 80px;
    background-color: #0099FF;
  }
  .menu ul li {
    list-style: none;
    float: left;
    width: auto;
    display: inline-block;
    margin-right: -4px;
  }
  .menu ul li a {
    display: block;
    height: 85px;
    line-height: 85px;
    padding-left: 30px;
    padding-right: 30px;
    font-size: 14px;
    font-family: 'Oswald', sans-serif;
    color: #ffffff;
    border-right: #0099FF solid 1px;
    text-transform: uppercase;
  }
  .menu ul li a:hover {
    background: #e1ece7;
    color: #1a202c;
  }
  .menu ul li a.active {
    background: #e1ece7;
    color: #1a202c;
  }
  .menu ul li ul {
    padding: 0;
    top: 48px;
    left: 0;
    width: 150px;
    -webkit-box-shadow: none;
    -moz-box-shadow: none;
    box-shadow: none;
    display: none;
    opacity: 0;
    visibility: hidden;
    -webkit-transiton: opacity 0.2s;
    -moz-transition: opacity 0.2s;
    -ms-transition: opacity 0.2s;
    -o-transition: opacity 0.2s;
    -transition: opacity 0.2s;
    z-index: 99999;
  }
  .menu ul li ul li {
    background: #555;
    position: relative;
    z-index: 99999999;
    width: 300px;
    color: #fff;
    text-shadow: 0 -1px 0 #000;
  }
  .menu ul li ul li:hover {
    background: #666;
  }
  .menu ul li:hover ul {
    display: block;
    opacity: 1;
    visibility: visible;
  }
  .header {
    margin: 0 auto;
    width: 960px;
    height: 120px;
  }
  .logo {
    width: auto;
    float: left;
    line-height: 120px;
  }
  .logo h1 {
    font-size: 24px;
    color: #d13f31;
    font-weight: normal;
  }
  .logo h1 span {
    color: #1a202c;
  }
  .social {
    float: right;
    margin-top: 45px;
  }
  .social ul li {
    list-style: none;
    float: left;
    margin-left: 15px;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="menu-wrap"&gt;
    &lt;div class="menu"&gt;
      &lt;ul&gt;
        &lt;li&gt;&lt;a href="index.html" class="active"&gt;home&lt;/a&gt;
        &lt;/li&gt;
        &lt;li&gt;&lt;a href="about.html"&gt;about&lt;/a&gt;
        &lt;/li&gt;
        &lt;li&gt;&lt;a href="services.html"&gt;Disease&lt;/a&gt;
        &lt;/li&gt;
        &lt;li&gt;&lt;a href="login.html"&gt;Search&lt;/a&gt;
        &lt;/li&gt;
        &lt;li&gt;&lt;a href="#"&gt;
      Portfolio&lt;/a&gt;
          &lt;ul&gt;
            &lt;li&gt;&lt;a href="asdqq.html"&gt;Web Design&lt;/a&gt;
            &lt;/li&gt;
            &lt;li&gt;&lt;a href="asd.html"&gt;Web Development&lt;/a&gt;
            &lt;/li&gt;
            &lt;li&gt;&lt;a href="asd.html"&gt;Illustrations&lt;/a&gt;
            &lt;/li&gt;
          &lt;/ul&gt;
        &lt;/li&gt;
      &lt;/ul&gt;
    &lt;/div&gt;
  &lt;/div&gt;
  &lt;div class="clearing"&gt;&lt;/div&gt;
  &lt;div class="header"&gt;
    &lt;div class="logo"&gt;
      &lt;h1&gt;Title&lt;/h1&gt;
    &lt;/div&gt;
    &lt;p&gt;&amp;nbsp;&lt;/p&gt;
    &lt;p&gt;&amp;nbsp;&lt;/p&gt;
    &lt;p&gt;&amp;nbsp;&lt;/p&gt;
    &lt;p&gt;&amp;nbsp;&lt;/p&gt;
    &lt;p&gt;&amp;nbsp;&lt;/p&gt;
    &lt;p&gt;&amp;nbsp;&lt;/p&gt;
    &lt;p&gt;&amp;nbsp;&lt;/p&gt;
  &lt;/div&gt;
  &lt;div class="clearing"&gt;&lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>Fiddle:</p>
  
  <p><a href="https://jsfiddle.net/darcychan/moyhthnd/" rel="nofollow">https://jsfiddle.net/darcychan/moyhthnd/</a></p>