body, html {
  height: 100%;
  margin: 0;
}

footer {
    position: fixed;
   left: 0;
   bottom: 0;
   width: 100%;
   background-color: red;
   color: white;
   text-align: center;
}

.encabezado{
  background-color: black;
  width: 100%;
  height: 150px;
  text-align: center;
  position: fixed;
  top: 0;
  margin-bottom: 10px;
  z-index: 100;
  border-bottom: 5px solid gray;
}

.hero-image {
  background-image: url("img/Baner.gif");
  width: 950px;
  height: 100px;
  background-repeat: no-repeat;
  background-size: cover;
  position: fixed;
  left: 50%;
  margin-left: -475px;
}

#contenedor {
  width: 57%;
  padding-top: 155px;
}

@media screen and (max-width: 960px) {
  .hero-image {
    left: 0;
    margin-left: 0px;
  }
}

  @media screen and (max-width: 800px) {
    #contenedor {
      width: 100%;
      padding-top: 105px;
    }

    .encabezado{
      height: 100px;
    }

    .hero-image {
      height: 75px;
      width: 800px;
    }
  }

  @media screen and (max-width: 500px) {

    .encabezado{
      height: 100px;
    }

    #contenedor {
      padding-top: 105px;
    }

    .hero-image {
      height: 75px;
      width: 500px;
    }
  }