浮动广告效果js

效果应用于 返回顶部按钮、左右对联广告 

display函数用于控制距离顶部多远，按钮出现

<script>
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;
}
suspendcode="<div id=\"goback\"><div id=\"full\" style='POSITION:absolute;TOP:300px;z-index:100; cursor:pointer;'><img onclick='window.scrollTo(0,0);'  src=\"style/images/goback.gif\"></div></div>"
document.write(suspendcode);
window.setInterval("heartBeat()",1);

function display(){
	var b_top= document.documentElement.scrollTop || window.pageYOffset || document.body.scrollTop;;
	if(b_top>200) document.getElementById("goback").style.display = "block";
	else document.getElementById("goback").style.display = "none";
	setTimeout("display();",100);
}
display();
</script>