<h2>box1에만 float:left를 적용</h2>
<div class="wrap">
  <div class="one float">box1</div>
  <div class="two">box2</div>
</div>

<h2>box1, box2 둘 다 float:left를 적용</h2>
<div class="wrap">
  <div class="one float">box1</div>
  <div class="two float">box2</div>
</div>
.wrap{
  border: 3px solid #999;
  font-size: 30px;
  margin-bottom: 30px;
}
.one{
  margin: 5px;
  background-color: lightpink;
}
.two{
  margin: 5px;
  background-color: lightblue;
}

.float{
  float: left;
}

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