#box01,
#box02,
#box03 {
  width: 100%;
  padding: 30px;
}

#box03 {
  padding-bottom: 0; /* 最後のboxに空きは不必要なので削除 */
}

#campaign {
  width: 100%;
  float: none; /* ここだけfloatを解除 */
}

External CSS

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External JavaScript

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