Include jQuery and Modernizr from a CDN and add local fallbacks in case the CDN fails. Versions written in HTML and HAML.

Local Fallback for jQuery and Modernizr

HTML
=====
<script type='text/javascript'>
  window.jQuery || document.write('<script src="js/jquery-1.7.1.js">\x3C/script>')
</script>
<script src='http://cdnjs.cloudflare.com/ajax/libs/modernizr/2.0.6/modernizr.min.js' type='text/javascript'></script>
<script type='text/javascript'>
  window.Modernizr || document.write('<script src="js/modernizr-2.0.6.js">\x3C/script>')
</script>


HAML
=====
%script(type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js")
:javascript
  window.jQuery || document.write('<script src="js/jquery-1.7.1.js">\x3C/script>')

%script(type="text/javascript" src="http://cdnjs.cloudflare.com/ajax/libs/modernizr/2.0.6/modernizr.min.js")
:javascript
  window.Modernizr || document.write('<script src="js/modernizr-2.0.6.js">\x3C/script>')