This took me forever to find!
This will work fine:
<!DOCTYPE html>
<head>
<title>Test me</title>
<script src="http://code.jquery.com/jquery-1.7.min.js"></script>
<script src="/assets/fbootstrap/js/bootstrap-twipsy.js"></script>
</head><body></body></html>
Where as this will not:
<!DOCTYPE html>
<head>
<title>Test me</title>
<script src="http://code.jquery.com/jquery-latest.js"></script>
<script src="/assets/fbootstrap/js/bootstrap-twipsy.js"></script>
</head><body></body></html>
It throws: "Uncaught TypeError: Cannot read property 'webkit' of undefined" in Chrome & FF.