lastScrollY=0;
function heartBeat(){
var diffY;
if (document.documentElement && document.documentElement.scrollTop)
diffY = document.documentElement.scrollTop;
else if (document.body)
diffY = document.body.scrollTop
else
{/*Netscape stuff*/}
percent=.1*(diffY-lastScrollY);
if(percent>0)percent=Math.ceil(percent);
else percent=Math.floor(percent);
document.getElementById("full").style.top=parseInt(document.getElementById("full").style.top)+percent+"px";
lastScrollY=lastScrollY+percent;
/*if(diffY == 0){document.getElementById("full").style.display = "none"}
else{document.getElementById("full").style.display = "block"}
}*/
if(diffY > 450){document.getElementById("full").style.display = "block"}
else{
	document.getElementById("full").style.display = "none"}
}

suspendcode="<div id=\"full\" style='display:none; width:15px; height:57px; POSITION:absolute; left:46%; top:200px; margin-left:500px;  z-index:100; text-align:center;'><a href='#'><img src='../THEMES/feng/script/top/btn_top.gif' border=0 /></a></div>"
document.write(suspendcode);
window.setInterval("heartBeat()",1);


<!--
//双击自动滚屏
var currentpos, timer;
function initialize() {
    timer = setInterval("scrollwindow()", 10); //设置滚动的速度
}
function sc() {
    clearInterval(timer);
}
function scrollwindow() {
    window.scrollBy(0, 1);
}
document.onmousedown = sc;
document.ondblclick = initialize;
-->