do you know of any Firefox extension which could put the browser itself in a "blocked" state (not accepting input from the user) for a certain amount of time (configurable by a timer) and then get back to normal behaviour?
I was in fact looking for a way to prevent me to go and check emails, news, .. on the Internet while doing other more important tasks, and although one could claim to use more "discipline", I think forcing the browser to not be able to receive inputs from the user could be a better solution :)