function img_scroll(g_id, ix_name, direction) {
  var curr = $($(ix_name).value);
  var nxt = following(curr, direction);
  Effect.Appear(nxt);
  Effect.Fade(curr);
  $(ix_name).value = nxt.id; 
}

function following(el, dir) {
  if (dir == 1) {
	t = el.nextSibling;
	if (t == null) {
	  ne = null;
	} else {
	  ne = t.nextSibling;
	}
  } else {
	t = el.previousSibling;
	if (t == null) {
	  ne = null;
	} else {
      ne = t.previousSibling;
	}
  }
  if (ne != null && ne.id != '') {
    return ne;
  } else {
    // no next element, start at beginning
    r = el;
    while (true) {
      if (dir == -1) {
    	t = r.nextSibling;
    	if (t == null) {
    	  e = null;
    	} else {
    	  e = t.nextSibling;
    	}
      } else {
    	t = r.previousSibling;
    	if (t == null) {
      	  e = null;
      	} else {
    	  e = t.previousSibling;
      	}
      }
      if (e != null && e.id != '') {
        r = e;
      } else {
        return r;
      }
    }
  }
}