/**
* javascript�ű�ʵ�ֻص�ҳ�涥��ʾ��
* @param acceleration �ٶ�
* @param stime ʱ���� (����)
**/
function gototop(acceleration,stime) {
   acceleration = acceleration || 0.1;
   stime = stime || 10;
   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 speeding = 1 + acceleration;
   window.scrollto(math.floor(x / speeding), math.floor(y / speeding));
 
   // ������벻ϊ��, �������ú���
   if(x > 0 || y > 0) {
       var run = "gototop(" + acceleration + ", " + stime + ")";
       window.settimeout(run, stime);
   }
}