* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  background-color: #fff;
}

a {
  display: block;
  margin: 0 auto;
}

.container {
  margin: 0 auto;
  overflow: hidden;
}

.container img {
  display: block;
  margin: 0 auto;
  max-width: 100%;
}

.container.medium–rectangle {
  width: 300px;
  height: 250px;
}

.container.large-mobile-banner {
  width: 320px;
  height: 50px;
}

.container.leaderboard {
  width: 100%;
  height: 50px;
}

.container img.only-mobile {
  display: block;
}

.container img.only-desktop {
  display: none;
}

@media only screen and (min-width: 768px) {
  .container img.only-mobile {
    display: none;
  }

  .container img.only-desktop {
    display: block;
  }

  .container.leaderboard {
    width: 728px;
    height: 90px;
  }
}