Top to bottom

Top to bottom

Hi am new, am trying to learn jquery in advance. 
Having issue to implement top to bottom. When i open the webpage, everything works properly, just the image which should be appeared in middle or bottom of the page, currently is shown only in the upside. 
Below is the code: 
<style>
#main {
float:left;
width:500px;
background:#c9c;
}
#sidebar {
position: fixed;
right:0px;
bottom:15px;
display:none;/*hid the button first*/
}
#sidebar a {
text-decoration:none;
border:0 none;
display:block;
width:31px;
height:155px;
}
#sidebar a:hover {
opacity:.8; /*mouse over fade effect*/
}
.hi {
clear:both;
}
</style>
<script src="http://code.jquery.com/jquery-1.7.2.min.js"></script>
<script src="http://code.jquery.com/ui/1.8.21/jquery-ui.min.js"></script>
<script src="jquery.ui.touch-punch.min.js"></script>
<script>
<script type="text/javascript">
jQuery(document).ready(function(){
var pxShow = 300;//height on which the button will show
var fadeInTime = 1000;//how slow/fast you want the button to show
var fadeOutTime = 1000;//how slow/fast you want the button to hide
var scrollSpeed = 1000;//how slow/fast you want the button to scroll to top. can be a value, 'slow', 'normal' or 'fast'
jQuery(window).scroll(function(){
if(jQuery(window).scrollTop() >= pxShow){
jQuery("#slidebar").fadeIn(fadeInTime);
}else{
jQuery("#slidebar").fadeOut(fadeOutTime);
}
});
 
jQuery('#slidebar a').click(function(){
jQuery('html, body').animate({scrollTop:0}, scrollSpeed); 
return false; 
}); 
});
</script>
</script>

</head>
<body>
<br>
abcabcabc
 <div id="main">
abcabcabc
        abcabcabcabcabcaabcabc
</div>
<div id class="low">
<div id="slidebar">
<a href="#"><img src="fb2.png" border="0" alt="Go to TOP" /></a>  
</div>
</div>
</body>
</html>