body {

overflow: hidden;

<a name="top" id="top"></a>

<div id="preloader">
  <div id="spinblock">
    <img id="spinner" src="images/spinner_big.gif" alt="" />
  </div>
</div>

#preloader {
  position:fixed; /* These 3 lines will set the preloader area fixed at the top in case overflow fails to hide */
  top:0;
  left:0;
  width:100%; /* Set the size of the preloader full screen */
  height:100%;
  background: #fff; /* If you have applied background image, you may use it. But keep the size as small as possible */
  z-index: 9999; /* Set the position of the preloader above all, greater value is more secure */
}

#spinblock {
  width: 75px; /* The spinner image area. Must be greater than the spinner_big.gif's width */
  margin: 250px auto; /* Align the spinner_big.gif at the middle of the screen */
}

#spinner {
  display: block;
  margin: auto auto;
}

{$stylesheets}

<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.1/jquery.min.js"></script>

{$newpmmsg}

<script type="text/javascript">
jQuery.noConflict();
jQuery(window).load(function() {
  jQuery('#preloader').fadeOut(300, function() {
    jQuery('body').css('overflow','visible');
    jQuery(this).remove();
  });
});
</script>