body {
background-image: url(images/fondo.gif);
}

#contenedor3 {
height: 520px;
width: 720px;
left: 50%;
top: 50%;
margin-left: -360px;
margin-top: -260px;
position: absolute;
background-color: #824E36;
}

h1 {
margin: 0; padding: 0;
background-color: #824E36;
}