div gap

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.css">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<body>

    <!-- Navigation -->
     <nav class="navbar navbar-default navbar-sticky-top topnav" role="navigation"> 
         <div class="container topnav"> 
             <div class="navbar-header">
                 <a class="navbar-brand topnav" href="#">Home</a>
            </div> 
             <!-- Collect the nav links, forms, and other content for toggling -->
             <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
                <ul class="nav navbar-nav navbar-right">
                    <li>
                        <a href="#">Imagery</a>
                    </li>
                    <li>
                        <a href="#">Education and Outreach</a>
                    </li>
                    <li>
                        <a href="index.html">Data Resources</a>
                    </li>
                </ul>
            </div> 
          </div>
     </nav>

    <div class="intro-header-homepage">
        <div class="container">
            <div class="row">
                <div class="col-lg-12">
                    <div class="intro-message">
                        <h1>Website Homepage</h1>
                    </div>
                </div>
            </div>

        </div>
    </div>
    
    <div class="row">
        <div class = "col-lg-6 col-lg-offset-3" text-align="center">
            <p class="p-homepage">Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt...

CSS

body,
html {
    width: 100%;
    height: 100%;
}

body,
h1,
h2,
h3,
h4,
h5,
h6 {
    font-family: "Lato","Helvetica Neue",Helvetica,Arial,sans-serif;
    font-weight: 700;
}
.p-homepage {
	padding: 0px 0px 30px 0px;
    font-weight: normal;
    font-size: 18px; 
	}	
  
.navbar-sticky-top { /* add navbar */
    background-color: #0D1721;
    border-color: #0D1721;
    margin-bottom: 0;
}

.topnav {
    font-size: 14px; 
}

.lead {
    font-size: 18px;
    font-weight: 400;
}

.intro-header-homepage {
    text-align: center;
    color: #f8f8f8;
	background: url(http://imgur.com/20qY3EH.jpg) no-repeat;
	background-size: 100% 80%;
}

.intro-message {
    padding-top: 20%;
    padding-bottom: 20%;
}

.intro-message > h1 {
    margin: 0;
    text-shadow: 2px 2px 3px rgba(0,0,0,0.6);
    font-size: 5em;
}