Basic Modal Window Popup with Pure CSS

This HTML link will open a modal popup that itself can be formatted using HTML and CSS. The modal window is written in pure CSS and requires no JavaScript or jQuery plugins.

The opacity of the Modal dialog is set to 0 (invisible) but the :target pseudo-class makes it visible with a lightbox style effect.

The HTML:

<a href="#open-modal">Open Modal</a>
<div id="open-modal" class="modal-window">
  <div>
    <a href="#modal-close" title="Close" class="modal-close">close &times;</a>
    <h1>CSS Modal</h1>
    <div>The quick brown fox jumped over the lazy dog.</div>
  </div>
</div>

The CSS:

.modal-window {
  position: fixed;
  background-color: rgba(200, 200, 200, 0.75);
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  z-index: 999;
  opacity: 0;
  pointer-events: none;
  -webkit-transition: all 0.3s;
  -moz-transition: all 0.3s;
  transition: all 0.3s;
}

.modal-window:target {
  opacity: 1;
  pointer-events: auto;
}

.modal-window>div {
  width: 400px;
  position: relative;
  margin: 10% auto;
  padding: 2rem;
  background: #fff;
  color: #444;
}

.modal-window header {
  font-weight: bold;
}

.modal-close {
  color: #aaa;
  line-height: 50px;
  font-size: 80%;
  position: absolute;
  right: 0;
  text-align: center;
  top: 0;
  width: 70px;
  text-decoration: none;
}

.modal-close:hover {
  color: #000;
}

.modal-window h1 {
  font-size: 150%;
  margin: 0 0 15px;
}