I just tried something rather trivial: get the source code of a web page (by saving it) and count how often a certain phrase occurs in the code.
Turns out, it doesn't work if that page uses Polymer / web components. Is this a browser bug?
Try the following: Go to http://www.google.com/design/icons/ and try to find star_half
in the code (the last icon on the page). If you inspect the element inside of Chrome or Firefox, it will lead you to
<i class="md-icon dp48">star_half</i>
but this won't be in the source if you copy the root node or save the html to disk.
Is there a way to get the entire code?