Live Example: (Read the CSS Newbie article)

Source Code: (Save the Source)

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>CSS Newbie Example: A Full-Width Centered Navigation Bar</title>
<style>
   #nav {
      width: 100%;
      float: left;
      margin: 0 0 1em 0;
      padding: 0;
      background-color: #f2f2f2;
      border-bottom: 1px solid #ccc;  }
   #nav ul {
      list-style: none;
      width: 800px;
      margin: 0 auto;
      padding: 0; }
   #nav li {
      float: left; }
   #nav li a {
      display: block;
      padding: 8px 15px;
      text-decoration: none;
      font-weight: bold;
      color: #069;
      border-right: 1px solid #ccc; }
   #nav li:first-child a {
      border-left: 1px solid #ccc; }
   #nav li a:hover {
      color: #c00;
      background-color: #fff; }

   /* This is just styling for this specific page. */
   body, html {
      margin: 0;
      padding: 0; }
   body {
      background-color: #555; 
      font: small/1.3 Arial, Helvetica, sans-serif;  }
   #wrap {
      clear: left;
      width: 800px;
      padding: 0;
      margin: 0 auto;
      background-color: #fff; }
   h1 {
      font-size: 1.5em;
      padding: 1em 8px;
      color: #333;
      background-color: #069;
      margin: 0; }
   #content {
      padding: 0 50px 50px; }      
</style>
</head>

<body>
<!-- Here's all the HTML you need to create this navigation bar. -->
<div id="nav">
   <ul>
      <li><a href="#">About Us</a></li>
      <li><a href="#">Our Products</a></li>
      <li><a href="#">FAQs</a></li>
      <li><a href="#">Contact</a></li>
      <li><a href="#">Login</a></li>
   </ul>
</div>
<!-- That's it! Everything else on the page follows below. -->

<div id="wrap">
   <h1>A Full-Width Centered Navigation Bar</h1>
   <div id="content">
      <p>The navigation bar above stays centered over our content area here, but still manages to stretch the full width of the browser window. And it only requires one extra div!</p>
      <p>The navigation bar design is a take off the <a href="http://www.cssnewbie.com/super-simple-horizontal-navigation-bar/">Super Simple Horizontal Navigation Bar.</a> To learn how to build this navigation bar, <a href="http://www.cssnewbie.com/full-width-centered-navigation-bar/">see the original article here.</a></p>
   </div>
</div>

</body>
</html>