// JavaScript Document
var lastScrollY = 0;
var output = '';
function checkScroll(){
	var diffPoint = 0;
	var percent = 0;
	if(document.documentElement && document.documentElement.scrollTop){
		diffPoint = document.documentElement.scrollTop;
	}else if(document.body){
		diffPoint = document.body.scrollTop;
	}
	percent=.1*(diffPoint-lastScrollY);
	if(percent>0){
		percent=Math.ceil(percent);
	}else{
		percent=Math.floor(percent);
	}
	document.getElementById("help_gotop").style.top=parseInt(document.getElementById("help_gotop").style.top)+percent+"px";
	lastScrollY=lastScrollY+percent;
	
	if(diffPoint > 300){
		document.getElementById("help_gotop").style.display = "block"
	}else{
		document.getElementById("help_gotop").style.display = "none"
	}
}
if(document.location.href=='http://www.aiens.cn/'){
	output = "<div id=\"help_gotop\" style='display:none; width:15px; height:57px; POSITION:absolute; left:50%; top:500px; margin-left:470px;  z-index:100; text-align:center;'><a href='#'><img src='http://www.aiens.cn/public/images/btn_top.gif' border=0 style='padding: 1px;' /></a></div>";
}else{
	output = "<div id=\"help_gotop\" style='display:none; width:15px; height:57px; POSITION:absolute; left:50%; top:390px; margin-left:470px;  z-index:100; text-align:center;'><a href='#'><img src='http://www.aiens.cn/public/images/btn_top.gif' border=0 style='padding: 1px;' /></a><br><br><a href='#comments'><img src='http://www.aiens.cn/public/images/btn_comment.gif' border=0 style='padding: 1px;' /></a></div>";
}

document.write(output);
window.setInterval("checkScroll()",1);