body {
  margin: 8px 0 0 0;
}
header,
footer {
  background: rgba(255, 255, 255, .9);
  position: fixed;
  top: 0;
  width: 100%;
}
footer {
  bottom: 0;
  top: inherit;
}
header p,
footer p {
  font-family: sans-serif;
  margin: 0;
  padding: .2em 0;
  text-align: center;
}
header p a,
footer p a {
  background-color: #E6E6E6;
  border: transparent;
  border-radius: 2px;
  box-sizing: border-box;
  color: rgba(0, 0, 0, .8);
  display: inline-block;
  font-size: 100%;
  margin-right: 1ex;
  padding: 6px .9rem;
  text-align: center;
  text-decoration: none;
  vertical-align: middle;
  white-space: nowrap;
}
footer p a {
  margin-right: .5ex;
  padding-right: 12px;
}
header p a:last-child,
footer p a:last-child {
  margin-right: 0;
}
header p a:hover,
footer p a:hover {
  background-image: linear-gradient(transparent, rgba(0, 0, 0, .05) 40%, rgba(0, 0, 0, .1));
  outline: 0;
}

main {
  display: inline-block;
  padding: 1.8em 0;
}
.bloc_nivose,
.bloc_arpa {
  float: left;
  padding: 5px;
}

/* taille initiale nivôse : 538x595 pixels */
/* Écran Samsung 28" du fixe à 168 (331 réels...) */
@media screen and (min-resolution: 168dpi) {
  .bloc_nivose img {
    max-width: 458px; /* 85% */
    max-height: 506px;
  }
}
/* Macbook à 192dpi (227 réels...)  */
@media screen and (min-resolution: 192dpi) {
  .bloc_nivose img {
    max-width: 404px; /* 75% */
    max-height: 446px;
  }
}
@media screen and (max-device-width: 538px) {
  body {
    margin: 0;
  }
  header,
  footer a.secondary {
    display: none;
  }
  main {
    padding: 0;
  }
  footer p a {
    padding: 6px .6rem;
  }
  .bloc_nivose img {
    max-width: 100%;
    max-height: 100%;
  }
}

.bloc_arpa p {
  font-family: sans-serif;
  font-size: 80%;
  font-weight: bold;
  margin: 0;
}
.bloc_arpa iframe {
  height: 235px;
  width: 400px;
}
@media screen and (max-width: 400px) {
  .bloc_arpa iframe {
    height: 48vw;
    width: 100%;
  }
}