Je toho asi dost, zkusil jsem hledat firefox extension count character a vyplivlo to třeba tohle:
http://get-business-online.com/blog/internet-marke ting/word-count-for-firefox/
https://addons.mozilla.org/en-US/firefox/addon/cou nt-word-n-character
https://addons.mozilla.org/en-us/firefox/addon/cou nt-words/
http://ask.metafilter.com/20336/Character-count-in -firefox-text-area
Atd.