This extensions function is included in Advanced Dork:
Provides a list of active window's ALT tags for use with Google's allintext Advanced search. Google can "see" alt tags which cannot be seen normally in the browser window, using these "Hidden" blurbs of text Advanced Google searches can be constructed.
Right-click any page, and the ALT tags are displayed in the context menu.
This tool has a very specific purpose, if you do not understand it's purpose contact me.