#contenu {
    width: 1024px;
}
.diz-contenu, article {
  width: 727px;
}

#image_accueil {
  	width: 90%;
	height: auto;
}

@media screen and (max-width: 550px){
	#image_accueil {
      width: 100%;
      height: auto;
  }
}