var AMOUNT=1; /* distance to scroll for each time */
var TIME=35; /* milliseconds */
var timer=null;
function scrollIt(v)
{
var direction=v?1:-1;
var distance=AMOUNT*direction;
window.scrollBy(0,distance);
}
function down(v)
{
  if(timer) { clearInterval(timer); timer=null; }
  if(v)timer=setInterval("scrollIt(true)",TIME);
}