title: Tool to identify which external javascript references are actually being used on a page
body: <p>I'm working on a website that currently has the same block of external JavaScript references on each page (added via a master page).  I'd like to go through the site and identify which script files are actually necessary for each specific page to improve performance.  Problem is there are a lot of pages and I'm not sure how to do it without resorting to manual trial and error process.</p>
  
  <p>Is there a Firefox plug-in or some other tool that will identify which JavaScript references could actually be called by the page and which are not necessary?</p>