I am proposing an extension based on your development of other firefox extensions for the benefit of the entire firefox community. This proposed extension, compatible with firefox 3.5 and later, would be useful to at least two groups of people:
1) parents monitoring internet use 2) anti-phishing feedback while surfing
Seems to only be able to take what is already part of the page title and modify it. I do not believe this userscript the way it is now will work to show the current tab's URL as a title prefix.