It’s best to load jQuery from a reliable CDN (like Google) for your code. Sometimes (rarely) the CDN you are pulling from may be down or possibly blocked by your web provider. You can add local link to insure your scripts properly function.
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="path/to/your/jquery.min.js"><\/script>')</script>Simple!