Untitled

<section>

  <div>div1</div>

  <div>div2</div>

  <div>div3</div>

  <div>div3</div>

</section>

<br />

<section>

  <div>div1</div>

  <div>div2</div>

  <div>div3</div>

</section>

section {

  width: 960px;

}

section::after {

  clear: both;

  content: " ";

  display: block;

  height: 0;

  visibility: hidden;

}

section div {

  float: left;

  width: 25%;

}

section {

  background-color: aqua;

  width: 960px;

  padding: 5px;

}

section div {

  background-color: white;

}