That Twitter logon page uses autocomplete = "off" to tell web browsers not to save the Username & Password; nothing to do with Robform.

This bookmarklet makes the browser ignore autocomplete="off" temporarily, allowing you to save passwords even on sites that use autocomplete="off".

Remember Password bookmarklet:
https://www.squarefree.com/bookmarklets/forms.html#remember_password

Or, you can use the Saved Passwords Editor extension for web sites where Firefox doesn't offer to save the Username /Password.
https://addons.mozilla.org/en-US/firefox/addon/60265/

I set autocomplete off in Firefox because Roboform will do this job. I set autocomplete off in IE as well, but Roboform can save the username and password when I have to.

Do you use Roboform? The problem is not with twitter only, the Roboform cannot save username and password for most of the websites in ff23 and ff24.

[SHIFT-ENTER] or [ALT] & Login after typing the username and password force Roboform to save the passcard. However, it just doesn't work in Firefox.

Thanks for your reply.

The problem solved after updated to Roboform 7.9.2