section#principal, aside
{
  border-radius: 0.5em;
  display: inline-block;
  margin: 0 auto;
  max-width: 100%;
  padding: 0.25em;
  vertical-align: top;
  width: 55%;
}

aside
{
  border: 1px solid;
  width: 35%;
  margin: 10px 10px;
}

iframe
{
  max-width: 100%;
  width: 450px;
  height: 250px;
}
#contenido
{
  max-width: 100%;
  margin: 0 auto;
}

@media(max-width: 1100px)
{
  #galeria, picture
  {
    width: 450px;
  }
}

@media(max-width: 900px)
{
  #galeria, picture
  {
    width: 350px;
  }
}

@media(max-width: 600px)
{
  #galeria, picture
  {
    width: 320px;
  }
}

@media(max-width: 450px)
{
  #galeria, picture
  {
    width: 220px;
  }
  aside
  {
    width: 200px;
  }
}