The main goal consists to view page source with external applications but you can also...
- open page source as DOM document, read faq
- open CSS and JS files present on page
- open images using your preferred image viewer (e.g. GIMP or ACDSee)
- open PDF links with Acrobat Reader or Foxit Reader or what you prefer
- edit textboxes content with your preferred editor and automatically see modified text on browser when you re-switch focus on it,this simplifies wiki pages editing, read faq
- open server side pages that generate the browser content, this simplifies web developer's debug, read server-faq
https://addons.mozilla.org/firefox/394/
