Brauche Hilfe beim zentrieren des Designs ^^

<div id="Streifen_unten"><div align="left"><a href="http://anime-community.de.tl/AC-Team.htm">Team</a>  │ 
<a href="http://cheese-game.de.tl/Impressum.htm">Impressum</a>  │
 <a href="http://anime-community.de.tl/Werbung.htm">Werbung</a>  │
 <a href="http://anime-community.de.tl/Partner.htm">Partner</a>  │
 <a href="http://anime-community.de.tl/Member-gesucht.htm">Bewerben</a>    │
Designed by Kenan D.</div></div>

#extraDiv1 {display: none;}
#extraDiv2 {display: none;}
#extraDiv3 {display: none;}
#extraDiv4 {display: none;}
#extraDiv5 {display: none;}
#extraDiv6 {display: none;}
#pre_header {display: none;}
#post_header {display: none;}

#nav_heading{display: none;}
div.header{display: none;}
h1#title{display: none;}
h2#title span {display: none;}

a{
color:#500000;
text-decoration: none;
font-size:13px;}

a:hover {
color: #4A9AF6;
font-size: 13px;
text-decoration: none;}

a:link {
color: #500000;
font-size: 13px;
text-decoration: none;}

a:active {
color: #4A9AF6;
font-size: 13px;
text-decoration: none;}

a:visited {
color: #500000;
font-size: 13px;
text-decoration: none;}


body {
margin: auto;
width:900px;
background-image: url(http://img.webme.com/pic/a/akatsuki-stream/backgroundas.png)
}

#header_container {
left:50%;
margin-left:-80px;
padding: 0px;
width: 1069px;
height: 250px;
background-color:#343434;
background-image:url(http://img.webme.com/pic/a/akatsuki-stream/headeras.png);
color:#FFFFFF;
font-size:13px;
border: 1px solid #FFFFFF;
-moz-border-radius: 10px;}


#content {
left: 50%;
margin-left:110px;
margin-top:-137px;
width: 680px;
heigth: auto;
color: #000000;
padding: 10px;
font-size: 14px;
font-family: Arial;
background-color:#343434;
background-image:url();
border: 1px solid #FFFFFF;
-moz-border-radius: 10px;}

#rechter_container {
position:absolute;left:232px;top:1321px;
margin-left:700px;
margin-top:0px;
width: 160px;
height: auto;
background-color:#343434;
background-image:url();
border:1px solid #FFFFFF;
color:#XXXXXX;
-moz-border-radius: 10px;}


#nav_container {
left: 50%;
margin-left: -80px;
margin-top:30px;
width: 160px;
height: auto;
background-color:#343434;
background-image:url();
border:1px solid #FFFFFF;
color:#XXXXXX;
-moz-border-radius: 10px;}


#Streifen_unten {
left: 50%;
margin-left:110px;
margin-top:auto;
width: 680px;
color: #000000;
padding: 10px;
font-size: 14px;
font-family: Arial;
background-color:#343434;
background-image:url();
border: 1px solid #FFFFFF;}

ul#nav{
width: 130px;
padding: 0px;
margin: 0px;}

li.nav_element{
list-style-type: none;
position: relative;
padding-bottom:15px;
padding-left:2px;
border: 1px;
width: 110px;
height: 20px;
text-align: left;}

li.nav_element a{
display: block;
padding:3px;
width: 115px;
height: 20px;
margin: 10px;
color: #F2F2F2;
font-weight: bold;
text-decoration: none;
background-color: #xxxxxx;
border: 0px solid #ffffff;
text-align: left;}

li.nav_element a:hover{
display: block;
color: transparent;
font-weight: bold;
text-decoration: none;
background-color: #XXXXXX;
color:#000000;
border: 0px solid #ffffff;
text-align: left;}