UI windows and mods are not allowed to save anything to disk. What you want could be done with the web browser if you were running a web server on your computer. Or, you could use one of the online notes tools like:
http://www.tadalist.com/
http://www.basecamphq.com/
http://docs.google.com/
Hmm, I couldn't get google docs to work but you might be able to use those others.