[Dilettante_Pro]

<div  class="nav_down" id="nav_down" style='position:fixed; left:100px;background-color:silver'>скролл вниз</div>
<div id = "container"></div>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.0/jquery.min.js"></script>
<script>
$(document).ready ( function ( ) {
    $('#nav_down').fadeIn('slow');  
    var win = $(window).height (),
         count = 1,
         content = "";
    for (var i=1;i<300;i++) content += i.toString() + "<br>";
    $('#container').html(content);
    $( '#nav_down' ).click ( function ( ) {
        $( 'body,html' ).animate ( {
           scrollTop: win * count
         } , 800 ) ;
         count++;
         return false ;
    } ) ;
} ) ;
</script>