<!-- Grab Google CDN's jQuery & jQuery UI. Fall back to local if necessary -->
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<script type="text/javascript">
    if (typeof jQuery == 'undefined') {
        document.write(unescape("%3Cscript src='/js/jquery-1.4.2.min.js' type='text/javascript'%3E%3C/script%3E"));
    }
</script>
<script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jqueryui/1.8.5/jquery-ui.min.js"></script>
<script type="text/javascript">
    if (typeof jQuery.ui == 'undefined') {
        document.write(unescape("%3Cscript src='/js/jquery-ui.min.js' type='text/javascript'%3E%3C/script%3E"));
    }
</script>

<!-- Grab Google CDN's jQuery & jQuery UI. Fall back to local if necessary -->
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<script>
  !window.jQuery && document.write('<script src="/js/libs/jquery-1.4.2.min.js"></script>'))
</script>
<script src="//ajax.googleapis.com/ajax/libs/jqueryui/1.8.5/jquery-ui.min.js"></script>
<script>
  !$.ui && document.write('<script src="/js/libs/jquery-ui-1.8.5.custom.min.js"></script>')
</script>

<!-- Grab Google CDN's jQuery & jQuery UI. Fall back to local if necessary -->
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<script>
  !window.jQuery && document.write(unescape('<script src="/js/libs/jquery-1.4.2.min.js"></script>'))
</script>
<script src="//ajax.googleapis.com/ajax/libs/jqueryui/1.8.5/jquery-ui.min.js"></script>
<script>
  !$.ui && document.write('<script src="/js/libs/jquery-ui-1.8.5.custom.min.js"></script>')
</script>

jQuery and jQuery UI CDN with fallback

jquery

JavaScript