div con position:fixed no me funciona

[yasahe]

Mira, este es el HTML

<div id="top_static">
<div>
<div class="headerbanner" id="headerbanner">
<div id="header">

</div>
</div>
<div>
<div id="menuv">
<div id="menu">

</div>
</div>


<div id="ban">
<div>

</div>

</div>
</div>
</div>
</div>

Y este es el CSS

#top_static{
margin: 0 auto 2px auto;
margin-bottom: 20px;
margin-top: 30px;
position: fixed;
float: left;
width: 980px;
height: 200px;
padding-bottom:15px;
}

#headerbanner {
width: 980px;
background: transparent url('../img/banner.jpg') ;
height: 130px;

}

#header {
float: left;
width: 67%;
text-align: right;
}

#menuv {
width: 980px;
height: 30px;
margin: 0 auto;
}

#menu{
float: left;
width: 980px;
height: 30px;
background: url(../img/img02.gif) repeat-x;
padding-bottom:15px;
}

#ban {
float: left;
width: 980px;
height: 35px;
background: url(../img/Simg02.gif) repeat-x;
background-color: white;
padding-bottom:15px;
}


Gracias por responder.