These work...
https://addons.mozilla.org/en-US/firefox/addon/3905/ Exif Viewer 1.55
https://addons.mozilla.org/en-US/firefox/addon/5673/ FxIF 0.4.1
These work...
https://addons.mozilla.org/en-US/firefox/addon/3905/ Exif Viewer 1.55
https://addons.mozilla.org/en-US/firefox/addon/5673/ FxIF 0.4.1