Rated 5 out of 5 stars
@Rico La Fonda, I just downloaded latest version (0.8.1.1) today and it's working fine with Firefox 5.0.1 and EditPad.
I include plain text files as well as html files in my website and this plugin is just great for offline editing of plain text files before refreshing them in Firefox (which also displays them). Maybe this is an unintended use, but sure works well for me. Of course its main purpose is to edit your html source code in your favorite editor while viewing in FF (after refreshing, of course).