Spinner on Center Page

<style>
div#loading {
  width: 100%;
  height: 100%;
  top: 0px;
  left: 0px;
  position: fixed;
  display: none;
  opacity: 0.7;
  background-color: #fff;
  z-index: 1999;
  color: #fbb450;
  text-align: center;
}
#loading-image {
  position: absolute;
  top: 50%;
  left: 40%;
  z-index: 2000;
}
</style>
<div id="loading">
<img id="loading-image" src="assets/img/loading_spinner.gif" alt="Loading..." />
</div>