<script type="text/javascript"> 
/** 
* 回到页面顶部 
* @param acceleration 加速度 
* @param time 时间间隔 (毫秒) 
**/
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; 

// 滚动条到页面顶部的水平距离 
var x = Math.max(x1, Math.max(x2, x3)); 
// 滚动条到页面顶部的垂直距离 
var y = Math.max(y1, Math.max(y2, y3)); 

// 滚动距离 = 目前距离 / 速度, 因为距离原来越小, 速度是大于 1 的数, 所以滚动距离会越来越小 
var speed = 1 + acceleration; 
window.scrollTo(Math.floor(x / speed), Math.floor(y / speed)); 

// 如果距离不为零, 继续调用迭代本函数 
if(x > 0 || y > 0) { 
var invokeFunction = "goTop(" + acceleration + ", " + time + ")"; 
window.setTimeout(invokeFunction, time); 
} 
} 
</script>