Fixed Nav

HTML:
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Drones</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css">
<link href='https://fonts.googleapis.com/css?family=Cuprum:400,700,400italic,700italic' rel='stylesheet' type='text/css'>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/js/bootstrap.min.js"></script>
<script src="btt index.js"></script>
<link rel="stylesheet" href="indexCSS.css" />
<h1 id="TITLE" class="text-center"> Kittatinny's Drone Information</h1>
<nav class="fixed-nav-bar">
<ul id="nav">
    <li><a href="index.html">Home</a></li>
    <li><a href="What Are Drones.html">What Are Drones</a></li>
    <li><a href="How Drones Work.html">How Drones Work</a></li>
    <li><a href="Buying a Drone.html">Buying a Drone</a></li>
    <li><a href="About Us.html">About Us</a></li>
  </ul>
</nav>
</head>

CSS:
@charset "utf-8";
/* CSS Document */
#TITLE {color: #1762a1; font-family: "Cuprum", sans-serif; font-size:80px;}
body { background:#393939}
/*Menu for Navigation (Duh)*/
#nav { list-style-type: none; height: 100px; padding: 0; margin: 0; }
#nav {text-align:center;}
#nav { list-style-type: none; height: 100px; padding: 0; margin: 0; }
#nav li { display:inline-block; position: relative; padding: 0; line-height: 100px; background: #393939 url(nav-bg.png) repeat-x 0 0; }
#nav li:hover { background-position: 0 -40px; }
#nav li a { display: block; padding: 0 15px; color: #fff; text-decoration: none; font-size: 40px; font-family: 'Cuprum', sans-serif; }
#nav li a:hover { color:#0F0 }
#nav li ul { opacity: 0; position: absolute; left: 0; width: 8em; background: #63867f; list-style-type: none; padding: 0; margin: 0; }
#nav li:hover ul { opacity: 1; }
#nav li ul li { float: none; position: static; height: 0; line-height: 0; background: none; }
#nav li:hover ul li { height: 30px; line-height: 30px; }
#nav li ul li a { background:#393939 }
#nav li ul li a:hover { background:#393939 }

.fixed-nav-bar {
  position: fixed;
  top: 0;
  left: 0;
  z-index: 9999;
  width: 100%;
  height: 50px;
  background-color: #393939;
}