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<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
#hid{
width: 50px;
height: 50px;
background: #FF0000;
opacity: 0;
position: fixed;
}
body{
height: 1500px;
}
</style>
<script src="http://code.jquery.com/jquery-1.9.1.js"></script>
<script>
$(document).ready(function(){
$(window).scroll(function(){
var bo = $(this).scrollTop();
var a = $("#hid").css('opacity')
$("#hid").html(bo);
if ( bo >= 200 && a == 0) {$("#hid").stop().animate({'opacity':'1'},500)};
if ( bo < 200 && a == 1) {$("#hid").stop().animate({'opacity':'0'},500)};
})
})
</script>
</head>
<body>
<div id="hid">
</div>
</body>
</html>