how to make disappear my <div> after a scroll to the top ? and reappear !

how to make disappear my <div> after a scroll to the top ? and reappear !

Hello

i have an image fixed on my page
it's a link to scroll to the top

i would like to make it disappear at the top and reappear when the scroll down ?

my code is actually very light, have you a solution ? thank you very much

  1. <!-- scrolltop -->
    <div id="scrolltop"><a href="#top"><img src="./wp-content/themes/blueprint/images/gotop.png" /></a></div>
    <script type="text/javascript">
    $(document).ready(function() {
    $('a[href=#top]').click(function(){$("html,body").animate({scrollTop:0},'slow');return false;});
    });
    </script>