var speed = 2;
var moveupvar = null;
var movednvar = null;
  
function getcontent_height(scontent) {
  return scontent.offsetHeight;
}

function scrolldown() {    
  var scontent = document.getElementById('scontent');
  
  if (parseInt(scontent.style.top) >= ((getcontent_height(scontent)*(-1)) + 400)) {
    scontent.style.top = (parseInt(scontent.style.top) - speed) + "px";
    movednvar = setTimeout("scrolldown()", 20);
  }
}

function scrollup() {    
  var scontent = document.getElementById('scontent');
  if (parseInt(scontent.style.top) < 0) {
    scontent.style.top = (parseInt(scontent.style.top) + speed) + "px";
    moveupvar = setTimeout("scrollup()", 20);
  }
}