Hi, I have created a slide down menu

Live Example:
http://adamhuxtable.com/testing_area/

It is working, however I want the content (purple area) to be pushed under the menu(blue area) when it appears.

Code Used:

HTML Code:
<!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="style.css" rel="stylesheet" type="text/css" />
<script type="text/javascript" src="js/jquery-1.6.1.min.js"></script>

<script type="text/javascript">
 
// When the DOM is ready, initialize the scripts.
jQuery(function( $ ){
 
// Get a reference to the container.
var worknav_container = $( "#worknav_container" );
 
 
// Bind the link to toggle the slide.
$( "a" ).click(
function( event ){
// Prevent the default event.
event.preventDefault();
 
// Toggle the slide based on its current
// visibility.
if (worknav_container.is( ":visible" )){
 
// Hide - slide up.
worknav_container.slideUp( 1000 );
 
} else {
 
// Show - slide down.
worknav_container.slideDown( 1000 );
 
}
}
);
 
});
 
</script>
</head>

<body>

<div id="top_container">
    <div id="header">
    	<nav>
       	  <ul>
            <li>Home</li>
                <li><a href="#">Work</a></li>
                <li>About</li>
                <li>Contact</li>
          </ul>
      </nav>
        <div id="twitter"><a href="http://www.twitter.com/adamhuxtable"><img src="assets/twitter_newbird_white.png" width="42" height="30" align="absmiddle" style="padding-right:10px;" /><span style="display:inline-block; float:right; margin-top:7px;">@adamhuxtable</span></a></div>
    </div>
    
    <div id="worknav_container">
    	<div id="worknav">
       Prototypes
        </div>
    </div>
</div>

<div id="body">
Adam
</div>

</body>
</html>
Code:
html, body, div, span, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
abbr, address, cite, code,
del, dfn, em, img, ins, kbd, q, samp,
small, strong, sub, sup, var,
b, i,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, figcaption, figure, 
footer, header, hgroup, menu, nav, section, summary,
time, mark, audio, video {
	margin:0;
	padding:0;
	border:0;
	outline:0;
	font-size:100%;
	vertical-align:baseline;
	font-family:Arial, Helvetica, sans-serif;
	background:transparent;
}

body {
    line-height:1;
}

article,aside,details,figcaption,figure,
footer,header,hgroup,menu,nav,section { 
    display:block;
}

nav li {
    display: inline;
list-style-type: none;
padding-right:25px;
}

blockquote, q {
    quotes:none;
}

blockquote:before, blockquote:after,
q:before, q:after {
    content:'';
    content:none;
}

a {
    margin:0;
    padding:0;
    font-size:100%;
    vertical-align:baseline;
    background:transparent;
}

/* change colours to suit your needs */
ins {
    background-color:#ff9;
    color:#000;
    text-decoration:none;
}

/* change colours to suit your needs */
mark {
    background-color:#ff9;
    color:#000; 
    font-style:italic;
    font-weight:bold;
}

del {
    text-decoration: line-through;
}

abbr[title], dfn[title] {
    border-bottom:1px dotted;
    cursor:help;
}

table {
    border-collapse:collapse;
    border-spacing:0;
}

/* change border colour to suit your needs */
hr {
    display:block;
    height:1px;
    border:0;   
    border-top:1px solid #cccccc;
    margin:1em 0;
    padding:0;
}

input, select {
    vertical-align:middle;
}

#top_container{
	width:100%;
	background:#000;
	height:40px;
}

#header{
	width:920px;
	margin:0 auto;
}

nav{
	color:#ffffff;
	margin-left:25px;
	padding-top:15px;
	padding-bottom:5px;
	
	font-size:14px;
	font-weight:bold;
	font-style:italic;
	color:#ffffff;
	float:left;
	list-style:none;
}

#twitter{
	float:right;
	padding-top:5px;
	padding-bottom:5px;
	font-size:14px;
	font-weight:bold;
	font-style:italic;
	color:#ffffff;
}

a:link{color:#ffffff;
text-decoration:none;
}

#worknav_container{
	clear:both;
	width:100%;
	background:#003366;
	height:150px;
	display:none;	
}

#worknav{
	width:920px;
	margin: 0 auto;
	padding: 25px 25px 80px 80px;
	color:#FFFFFF;
}

#body{
	width:100%;
	background:#993366;
	float:left;
	margin-top:200px;
}