A Pen by Captain Anonymous.

An-Anonymous-Pen.markdown

An Anonymous Pen

A Pen by Secret Sam on CodePen.

License.

index.html

<div class="center-div"></div>

style.css

.center-div
{
  position: absolute;
  margin: auto;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  width: 100px;
  height: 100px;
  background-color: #ccc;
}