alt Hacker NewsI've never had one tell me; they just don't work, or they get stuck in a loop until they consume all my RAM and the gecko engine crashes. That is, assuming they even show me the page, instead of telling me to go away because they they think I'm a bot.
A few years ago I was maintaining the website for a major brand whose products you probably use. To my horror the website did not support Firefox. I gave them a very minimal estimate on what it would cost to support Firefox along with the estimated percentage of Firefox users in their target market. They were not interested.