html, body{
text-align:center;
width: 650px;
height: 650px;
margin: 0 auto;
background-color: #FFFFFF;
}

div#conteneur{
  width: 600px;
  height: 600px
  background-color: #FFFFFF;
  background-image:url(intro.png);
  background-repeat: no-repeat;
  margin-left: auto;
  margin-top: auto;
}

div#contenu{
  width: 590px;
  padding: 20px 20px 7px 10px
}