Good Evening,
I am using this script:

<style>
a.back-to-top {
outline: 0;
display: none;
width: 60px;
height: 60px;
text-indent: -9999px;
position: fixed;
z-index: 999;
right: 20px;
bottom: 20px;
background: #000000 url("up-arrow.png") no-repeat center 43%;
opacity: 1.0;
-webkit-border-radius: 0px;
-moz-border-radius: 0px;
border-radius: 0px;
}
</style>
<script type="text/javascript">
$('body').prepend('<a href='./index-arrow/up-arrow.png' class="back-to-top">Back to Top</a>');
</script>
<a href='./index-arrow/up-arrow.png' class="back-to-top">Back to Top</a>

Thanks for the share.