var btn=document.getElementById('gotopbtn');
var d=document.documentElement;
backTop=function (){
	window.onscroll=set;
	btn.onclick=function (){
		btn.style.display="none";
		window.scrollTo(0,0)
		this.timer=setInterval(function(){
			d.scrollTop-=Math.ceil(d.scrollTop*0.1);
			if(d.scrollTop==0) clearInterval(btn.timer,window.onscroll=set);
		},10);
	};
	function set(){
		//alert(d.scrollTop);
		if(d.scrollTop==0)
		{
			btn.style.display="none";
		}
		else
		{
			btn.style.display="block";
		}
		document.getElementById("gotopbtn").style.top=document.documentElement.clientHeight-150+parseInt(document.documentElement.scrollTop)+"px";
	}
};
backTop();
if(navigator.appName=="Microsoft Internet Explorer"){//window¾ÖÖÐ
	document.getElementById("gotopbtn").style.top=document.documentElement.clientHeight-150+parseInt(document.documentElement.scrollTop)+"px";
	
}
else{
	//document.getElementById("gotopbtn").style.position="fixed"; 
	document.getElementById("gotopbtn").style.top=document.documentElement.clientHeight-150+"px";
	//document.getElementById("gotopbtn").style.right = "12%";
}