<div class="box1">
	<div class="box2">黄色のbox2を、box1に対して、幅を50%、高さを50%にしたらこうなるよ</div>
</div>	
.box1 {
  background: skyblue;
  width: 200px;
  height: 200px;
}

.box2 {
  background: yellow;
  width: 50%;
  height: 50%;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.