Put options parameter in your tooltip().
$(document).tooltip({ position: { my: "bottom", at: "top" } });
Reference jQuery UI:
<script type="text/javascript" src="http://code.jquery.com/ui/1.10.3/jquery-ui.min.js"></script>
Here's the JSFiddle code: http://jsfiddle.net/2gLm5/4/
If your browser is incompatible, just use a third-party library like Bootstrap