title: What's the actual font used by Firefox to render an element?
body: <p>Yes, I know about addons such as Firebug or the Web Developer Toolbar that allow one
  to see the font-family specification pertaining to a specific element, but how can I
  find out which actual font is Firefox using to render the element?</p>
  
  <p>To give you an example, suppose I declare, say <code>font-family: "Georgia", "Verdana", serif;</code>.
  Now, the <em>Georgia</em> font is not installed in the system, and Firefox thus picks the next on
  the list (<em>Verdana</em>).  Is there some addon out there that will give me access to this info?</p>
  
  <p>Note that I need this functionality for development, not for detection at runtime inside Javascript.</p>