This is for security reasons. In the case of banking sites after every browser exit next time you need to enter again.

Some web sites, like banks, tell browsers to not record or enter password information. Go to the Mozilla Add-ons Web Page (There’s a lot of good stuff here)
and look around for something to help you. I use an add-on called Remember Passwords

Experimental Patches the original Login Manager to allow saving of passwords on forms which otherwise suppress it.


You can also check out form filling add-ons.

The current Firefox release has a pref to override autocomplete=off, so you shouldn't need extensions or bookmarklets

• You can toggle the signon.overrideAutocomplete pref to true on the about:config page.