如何在導航欄中放置背景

我試圖在這個導航欄後面放置一個純色的白色背景，所以當它滾動時它不會顯示它背後的內容。如何在導航欄中放置背景

CodePen Example of Bar | http://codepen.io/enoughsev/pen/vAJCo

<div id="header"> 
    <img id="nav_img" src="Graphics/nav_img.svg" height="122" width="201" alt="Lanier Canoe and Kayak Club logo"/> 
     <div id="nav_bar" style:"color:#FFF;"> 
      <header id="title">Lanier Canoe and Kayak Club</header> 
      <ul id="nav_words"> 
      <a href="#" id="menu_item"><li class="selected items">Home</li></a> 
      <a href="#" id="menu_item"><li class="items">About Us</li></a> 
      <a href="#" id="menu_item"><li class="items">Programs</li></a> 
      <a href="#" id="menu_item"><li class="items">Rentals</li></a> 
      <a href="#" id="menu_item"><li class="items">Contact Us</li></a> 
      </ul> 
     </div> 
</div>

理論上我應該能夠只是把

#header { 
    width: 100%; 
    height: 150px; 
    padding-bottom:20px; 
    background-color:#FFFFFF; 
    border: 
    z-index: 3; 
    color:white; 
}

，它正常工作正確嗎？

來源

2014-01-30 enoughsev