Code
<style type='text/css'>#top-bottom_middle {position:fixed;_position:absolute;bottom:2px;right:10px;
clip:inherit;_top:expression(document.documentElement.scrollTop+document.documentElement.clientHeight-this.clientHeight);_left:expression
(document.documentElement.scrollLeft+ document.documentElement.clientWidth - offsetWidth);}</style>
<script type='text/javascript'>var maxWidth = (document.body.clientWidth);
var maxHeight = (document.body.clientHeight);</script>
<div id='top-bottom_middle'><a href='javascript:top.window.scrollTo(0,0)' title='Lên đầu trang'>
<img alt='Đầu trang' border='0' src='http://cc1.upanh.com/27.4.34259920.dtI0/len.png'/></a><br/><a href='javascript:window.scrollTo(maxWidth,maxHeight/2)' title='Giữa trang'>
<img alt='Giữa trang' border='0' src='http://www.photo.yeah1.com/images/smilies/tettet/ok.gif'/></a>
<br/><a href='javascript:window.scrollTo(maxWidth,maxHeight*10000)' title='Xuống cuối trang'>
<img alt='Cuối trang' border='0' src='http://cC2.upanh.com/27.4.34259921.cvn0/xuong.png'/></a>
</div>
Demo: