Bir de böyle denermisin.

Html: (form alanı yazdığım yere form gelecek.)

<!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=utf-8" />
<title>Untitled Document</title>
<link href="Stil.css" rel="stylesheet" type="text/css" />
</head>

<body>

	<div id="Wrapper">
    
    	<div id="Header">
        
        	<div id="Logo_Header">
            
            <img src="Resimler/Logo.jpg" />
            
            </div>
        
        	<div id="Menu">
        
       			<div id="Menu_Menu">
        
        			<ul>
            
            		<li class="yan_cizgi"><a href="#">Ana Sayfa</a></li>
            		<li class="yan_cizgi"><a href="#">Üye Kayıt</a></li>
            		<li class="yan_cizgi"><a href="#">Üye Girişi</a></li>
            		<li class="yan_cizgi"><a href="#">Ulaşım</a></li>
            		<li class="yan_cizgi"><a href="#">Harita</a></li>
            		<li class="yan_cizgi"><a href="#">İletişim</a></li>  
            
    				</ul>        
                    
      			</div>
        
      		</div>
        
        </div>
    
    <div id="content">form alanı</div>
    	<div id="Footer">
    
    <center><br />Footer</center>
    
    </div>
    </div>



</body>
</html>
Css:

body {
background-image: url(Resimler/back.png);
background-repeat: repeat;
margin: 0px;
padding: 0px;
}
form {
display: block;
margin: 0px;
padding: 0px;
float:left;
}
td {
font-family: Tahoma;
font-size: 9px;
font-weight: normal;
color: #000000;
}#Wrapper {
background-color: #FFFFFF;
padding: 0px;
width: 920px;
margin-top: 0px;
margin-right: auto;
margin-bottom: 0px;
margin-left: auto;
}
#Header {
display: block;
padding: 0px;
width: 920px;
margin-top: 0px;
margin-right: auto;
margin-bottom: 0px;
margin-left: auto;
}
#Logo_Header {
display: block;
padding: 0px;
width: 920px;
margin-top: 0px;
margin-right: auto;
margin-bottom: 0px;
margin-left: auto;
height: 100px;
}
#Menu {
display: block;
padding: 0px;
width: 920px;
margin-top: 0px;
margin-right: auto;
margin-bottom: 0px;
margin-left: auto;
}
#Menu_Menu {
margin: 0px;
float: left;
width: 920px;
display: block;
height: 30px;
padding: 0px;
background-image: url(Resimler/Menu/menu_bg.png);
background-repeat: repeat-x;
}
#Menu_Menu li {
display: block;
float: left;
margin: 0px;
padding-top: 0px;
padding-right: 0px;
padding-bottom: 0px;
padding-left: 0px;
height: 30px;
list-style-type: none;
}

#Menu_Menu ul {
float: left;
width: 800px;
display: block;
height: 30px;
padding: 0px;
margin: 0px;
}
#Menu_Menu a {
font-family: Tahoma;
font-size: 12px;
font-weight: bold;
color: #FFFFFF;
line-height: 30px;
text-decoration: none;
padding-right: 10px;
padding-left: 20px;
display: block;
background-image: url(Resimler/Menu/beyaz_ok.gif);
background-repeat: no-repeat;
background-position: left center;
}
#Menu_Menu a:hover {
font-family: Tahoma;
font-size: 12px;
font-weight: bold;
color: #FFFFFF;
line-height: 30px;
padding-left: 20px;
display: block;
background-color: #0272B0;
padding-right: 10px;
}
.yan_cizgi {
border-right-width: 0px;
border-right-style: dotted;
border-right-color: #8F0A0A;
}
#Footer {
font-family: Tahoma;
font-size: 11px;
font-style: normal;
font-weight: bold;
color: #FFFFFF;
background-color: #666666;
display: block;
padding: 0px;
height: 50px;
width: 920px;
margin-top: 0px;
margin-right: auto;
margin-bottom: 0px;
margin-left: auto;
clear:both;
}
#content{
width:920px;
float:left;
text-align:left;}