text: 
  function goTop(acceleration, time) { 
  acceleration = acceleration || 0.1; 
  time = time || 16; 
   
  var x1 = 0; 
  var y1 = 0; 
  var x2 = 0; 
  var y2 = 0; 
  var x3 = 0; 
  var y3 = 0; 
   
  if (document.documentElement) { 
  x1 = document.documentElement.scrollLeft || 0; 
  y1 = document.documentElement.scrollTop || 0; 
  } 
  if (document.body) { 
  x2 = document.body.scrollLeft || 0; 
  y2 = document.body.scrollTop || 0; 
  } 
  var x3 = window.scrollX || 0; 
  var y3 = window.scrollY || 0; 
   
  // ��������ҳ�涥����ˮƽ���� 
  var x = Math.max(x1, Math.max(x2, x3)); 
  // ��������ҳ�涥���Ĵ�ֱ���� 
  var y = Math.max(y1, Math.max(y2, y3)); 
   
  // �������� = Ŀǰ���� / �ٶ�, ��Ϊ����ԭ��ԽС, �ٶ��Ǵ��� 1 ����, ���Թ��������Խ��ԽС 
  var speed = 1 + acceleration; 
  window.scrollTo(Math.floor(x / speed), Math.floor(y / speed)); 
   
  // ������벻Ϊ��, �������õ��������� 
  if(x > 0 || y > 0) { 
  var invokeFunction = "goTop(" + acceleration + ", " + time + ")"; 
  window.setTimeout(invokeFunction, time); 
  } 
  } 
  