<ul>
  <li>1.左カラム</li>
  <li>2.右カラム</li>
</ul>
ul {
  list-style: none;
  width: 100%;
  padding: 5px;
}

ul li{
  background: #eee;
  border: 1px solid #ccc;
  display: block;
  width: 100%;
  height: 500px;
}

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