* { padding: 0; margin: 0; }

body {
 font-family: Arial, Helvetica, sans-serif;
 font-size: 13px;
 background-image:url(fondo.jpg);
 background-repeat: repeat-y;
 background-position:center;
}

#wrapper { 
 margin: 0 auto;
 width: 900px;
}