Some webpages manage to write an incorrect value into the password that is saved by the "would you like to update this login?" (if you've already saved a working login) or "would you like firefox to remember this login?" (if you haven't previously saved a working login). In each case, clicking the "show...." checkbox shows some value other than what was actually entered/used, causing the remembered login to fail. The only way I've been able to work around this is to use the "Saved Password Editor" extension to fix what was saved, then to answer "no" to all future offers to update the login. Here is one such page: https://mycw32.eclinicalweb.com/portal3397/jsp/100mp/login_otp.jsp You don't need a valid account to observe the effect. Another is the the login page of the Linksys 2500 wireless router, "Linksys E2500 Firmware Version: 2.0.00 " I am pretty sure the web pages are doing this intentionally - I've only seen this behavior in these 2 places, but it is very consistent in those places; in the case of the Linksys, it has been this way for 4 - 5 years.