<a href="javascript://" onclick="doTop(30);">Up</a>  

<script type="text/javascript">  
function doTop(speed) {  
   var u = document.body;  
   speed = speed || 15;  
   x = setInterval(function () {  
    if (u.scrollTop == 0) {  
     clearInterval(x);  
    }  
    u.scrollTop = parseInt(u.scrollTop) - speed;  
   },  
   10);  
}  
</script>