Mettre une image de fond

Bonjour,

j'aimerais savoir comment mettre une image de fond sur ce code

@charset "utf-8";
/* CSS par Blackers */

body {
font: 100% Verdana, Arial, Helvetica, sans-serif;
background: #A5A2A9;
margin: 0;
padding: 0;
text-align: center;
color: #ffffff;
font-size: 12px;
}

#site {
text-align:left;
width: 802px;
margin: auto;
border: 1px solid #000000;
background: #737373;
}

#header {
background: #737373 url(images/header.jpg) no-repeat;
margin: 0;
padding: 0;
height: 260px;
}

#header h1 {
margin: 0;
padding: 10px 0;
}

#contenu {
padding: 20px;
}

div#left {
float: left;
width: 518px;
margin: 0px;
padding: 0px;
margin-bottom: 25px;
margin-left: 10px;
}

div#right {
width:199px;
float:left;
margin-bottom: 25px;
margin-left: 30px;
}

div#bloc{
border:solid 1px #000000;
margin-left:0;
margin-right:15px;
background: #737373 url(images/news.jpg) no-repeat;
padding-top: 30px;
padding-bottom: 15px;
padding-right: 18px;
padding-left: 18px;
}

div#menu{
border:solid 1px #000000;
margin-left:0;
margin-right:15px;
background: #737373 url(images/menu.jpg) no-repeat;
padding-top: 50px;
padding-bottom: 15px;
padding-right: 18px;
padding-left: 18px;
}

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

div#menu ul{
margin:0px;
padding:15px;
list-style-image: url ("images/fleche.gif");
}

div#menu li{
list-style-image: url ("images/fleche.gif");
padding-bottom: 8px;
}

#footer {
margin-left: 30px;
margin-right: 30px;
margin-bottom: 25px;
border:solid 1px #000000;
height: 30px;
clear: both;
}

#footer p {
padding:8px;
margin:0px;
text-align: center;
}

img { border: 0; }

cordialement .