为什么我的水平菜单没有浮动到右边？

您知道为什么我的水平菜单向右浮动吗？您可以在此处实时查看。

<header>

  <nav>
    <ul>
      <li><a href="#">Home</a></li>
      <li><a href="#">Work</a>
        <ul>
          <li><a href="#">Résumé</a></li>
          <li><a href="#">Portfolio</a></li>
        </ul>
      </li>
      <li><a href="#">Play</a>
        <ul>
          <li><a href="#">Experiments</a></li>
          <li><a href="#">Utilities</a></li>
        </ul>
      </li>
      <li><a href="#">Contact</a></li>
    </ul>
  </nav>
  <div id="news_box" style="max-width: 400px; float: right; text-align: left;"></div>

</header>

CSS：

body {
  background-color: rgb(255, 255, 255);
  font-family: Helvetica;
  font-size: 16px;
  font-weight: 400;
  line-height: 1.38;
  color: rgb(21, 84, 244);
  margin: 0;
  margin: 0;
    padding: 0;
    border: 0;
}

header {
  width: 100%;
  height: 600px;
  min-height: 300px;
  margin-right: auto;
  margin-left: auto;
  background-image: url('http://lorempixel.com/output/nature-q-c-1020-711-1.jpg');
  background-size: cover;
  background-position: center center;
  background-color: rgb(222, 222, 222);
}

h1 {
  width: 100%;
  margin-top: 39px;
  margin-right: auto;
  margin-left: auto;
  font-size: 37px;
  font-weight: 400;
  line-height: 1.38;
  text-align: center;
  color: rgb(0,0,0);
}


.blablatext {
  margin-top: 16px;
  margin-right: auto;
  margin-left: auto;
  font-weight: 400;
  line-height: 1.38;
  text-align: center;
  color: rgb(21, 84, 244);
}

nav {margin: 20px auto}
nav ul li {display: inline-block; margin-right: -4px; margin-left: 5px; vertical align: top}
nav a {padding: 7px 10px; text-decoration: none; color: rgba(255,255,255,0.9); background: rgba(0,0,0,0); border-radius: 5px; font-weight: 300; text-transform: uppercase; letter-spacing: 1.5px; font-size: 13px}
nav a:hover {background: rgba(0,0,0,0.25)}
.activeNav {background: rgba(0,0,0,0.25)}
nav ul li ul {position: absolute; display: block; margin-top: 5px; border-radius: 5px; border-top-left-radius: 0; background: none; padding-top: 5px}
nav ul li ul li {display: block; float: none; margin: 0; padding: 0}
nav ul li ul li a {display: block; text-align: left; color: rgba(255,255,255,0.9); text-shadow: 0 1px rgba(0,0,0,0.33); padding: 10px}
nav ul li ul li a:hover {background: rgba(20,150,220,0.5); color: white; text-shadow: 0 1px rgba(0,0,0,0.5)}
.hover a {display: block;}
.hover span { color: rgba(255,255,255,0.9); background: rgba(20,150,220,0.5); border-radius: 5px; position: absolute; display: block; margin: 5px 0 0 -57px; padding: 10px; font-size: 13px; font-weight: 300; letter-spacing: 1.5px; text-transform: uppercase; text-align: center; cursor: default;}