'JSON' and 'jQuery' still undefined in Internet Explorer 7 and 8
jQuery 2.0 drops support for IE 6, 7 and 8, and is only meant for when you know you don't need to support those browsers. For most people the correct solution is to use jQuery 1.x instead, which is still officially supported:
<script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>