var getDiv=document.getElementById('returntop');
getDiv.onclick=function(){
	window.scrollTo(0,0);
}
window.onscroll=function(){
	if(document.documentElement.scrollTop){
		getDiv.style.display="block";
	}else if(document.body.scrollTop){
		getDiv.style.display="block";
	}else{
		getDiv.style.display="block";	
	}
}
function getWinSize(){
	var winHeight=window.innerHeight,winWidth=window.innerWidth;
	if(document.documentElement.clientHeight){
		winHeight=document.documentElement.clientHeight;
		winWidth=document.documentElement.clientWidth;
	}else{
		winHeight=document.body.clientHeight;
		winWidth=document.body.clientWidth;
	}
    var height=winHeight-50;
	var width=winWidth-100;
	getDiv.style.top=height+"px";
	getDiv.style.left=width+"px";
}
getWinSize();
window.onresize=getWinSize;