But there is still one thing that´s a problem...You have to type one line more in your head.
So that the complete Script part have to sound like this:
<script src="http://code.jquery.com/jquery-1.10.2.min.js"></script>
<script src="//ajax.googleapis.com/ajax/libs/jquery/2.0.2/jquery.min.js"></script>
<script>
$(document).ready(function () {
$(window).scroll(function () {
if ($(this).scrollTop() > 100){$('.scrollup').fadeIn();}
else {$('.scrollup').fadeOut();}});
$('.scrollup').click(function () {
$("html, body").animate({scrollTop: 0
}, 600);
return false;});});
</script>
and than it should work ;D