Design Flexible para CSS

lli.nav_element{display: none;}
li.nav_element a{display: none;}
h1#title{display: none;}
h2#title span {display: none;}
div.header{display: none;}
li.nav_element{list-style-type: none;}
li.nav_element{display: none;}

h1 {
font-size: 2em;
margin: 0.67em 0;
}

nav ul,
nav ol {
list-style: none;
list-style-image: none;
}

.forumtabelle {
width: 1000px;
}

body {
margin: 0;
font-size: 1em;
line-height: 1.4;
font-family: 'Open Sans', sans-serif;
background: #161616;
font-size: 16px;
line-height: 1.4;
background-color: #EEE;
}

.container {
background: #121212;
color: #e6e6e6;
width: 1040px;
margin: 0 auto;
box-shadow: 0px 0px 10px 0px rgba(0, 0, 0, 1);
float: left;
}

.containerMain {
width: 1215px;
margin: 0 auto; 
}

.header {
background-image: url(http://img.webme.com/pic/m/master-nemesis/fheader.jpg);
text-transform: uppercase;
letter-spacing: 2px;
font-weight: bold;
border: 1px solid #aaa;
height: 200px;
}

.title {
color: #FFB700;
margin: 0;
padding: 24px 48px 0;
letter-spacing: 4px;
font-size: 48px;
position: relative;
z-index: 1;
overflow: hidden;
text-overflow: ellipsis;
top: 0px;
left: 0px;
}

.nav {
font-size: 12px;
padding-bottom: 24px;
}

.nav > ul > li {
float: left;
position: relative;
padding: 8px 24px 8px 24px;
}
.nav > ul > li > ul > li {
background: #4b7082;
padding: 6px 16px 6px 8px;
position: relative;
z-index: 1000;
}
.nav > ul > li > ul {
left: 0;
top: 28px;
visibility: hidden;
}
.nav > ul > li:hover > ul,
.nav > ul > li:active > ul {
visibility: visible;
}

.nav ul {
  margin: 0;
  padding: 0;
  position: absolute;
}
.nav > ul {
  background: rgba(0, 0, 0, 0.5);
  box-shadow: 0px 2px 3px -1px rgba(0,0,0, 0.51);
  position: relative;
  z-index: 2;
  float: left;
  width: 100%;
  position: relative;
  /* mit top l√§sst sich die nav vertikal verschieben */
  top: 0px;
}
.nav a,
.nav a:visited {
  text-decoration: none;
  color: #fff;
}
.nav a:hover,
.nav a:active {
  color: #ff0;
}

.content {
width: 1040px;
float: left;
padding: 32px;
min-height: 400px;
}

.footer {
  clear: both;
  border-top: 1px solid #4b7082;
  min-height: 48px;
  padding: 16px;
  font-size: 10px;
}

.top {
    width: 40px;
}

#webme_footer_textlink_dont_hide {
margin: 600px 0px 0px 400px;
}

<div class="containerMain">
<div class="top"><br />
</div>
<div class="container">
<header class="header">
<h1 class="title">Master Nemesis</h1>
<nav class="nav clearfix">
<ul>
<li id="checked_menu"><a href="#ENLACE">Principal</a>
</li>                   
<li><a href="/Contacto.htm">Contacto</a>
</li>                   
<li><a href="/Foro/index.htm">Foro</a>
</li>                   
<li><a href="#">Copyright</a>
</li>                   
<li><a href="#">Prueba</a>
</li>                   
</ul>     
</nav>
<div id="fb-root"></div>
<script>(function(d, s, id) {
  var js, fjs = d.getElementsByTagName(s)[0];
  if (d.getElementById(id)) return;
  js = d.createElement(s); js.id = id;
  js.src = "//connect.facebook.net/es_ES/all.js#xfbml=1";
  fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));</script>
<div id="likeButton" align="right">
<div class="fb-like" data-href="http://facebook.com/imastern" data-width="450" data-layout="button_count" data-show-faces="true" data-send="false"></div>
</div>
</header>
<section class="content">

</section>
<footer class="footer">
Diseño hecho por <i>Master Nemesis</i> para css design</footer>
</div>