lastScrollY = 0;
function heartBeat(){ 
var diffY;
var floatImg = document.getElementById("etang_left"); 
var floatleftImg = document.getElementById("etang_right"); 

if (document.documentElement && document.documentElement.scrollTop)
diffY = document.documentElement.scrollTop;
else if (document.body)
diffY = document.body.scrollTop
else
     {/*Netscape stuff*/}

//alert(diffY);
percent=.1*(diffY-lastScrollY); 
if(percent>0)percent=Math.ceil(percent); 
else percent=Math.floor(percent); 
//alert();
if ((screen.width <= 800) && (screen.height <= 600))
{
document.getElementById("leftDiv").style.top = parseInt(document.documentElement.scrollTop) - 30 +percent+"px";
document.getElementById("rightDiv").style.top = parseInt(document.documentElement.scrollTop) - 30 +percent+"px";
}
else
{
document.getElementById("leftDiv").style.top = parseInt(document.documentElement.scrollTop) + 100 +percent+"px";
document.getElementById("rightDiv").style.top = parseInt(document.documentElement.scrollTop) + 100 +percent+"px";
floatImg.style.top=parseInt(document.documentElement.scrollTop) + 420 +percent+"px";
floatleftImg.style.top = parseInt(document.documentElement.scrollTop) + 420 +percent+"px";
}


lastScrollY=lastScrollY+percent; 
//alert(lastScrollY);
}

//下面这段删除后，对联将不跟随屏幕而移动。
window.setInterval("heartBeat()",100);
function closeLeft()
{
	document.getElementById("leftDiv").style.visibility='hidden';
}
function closeRight()
{
	document.getElementById("rightDiv").style.visibility='hidden';
}