Can I block saving passwords by default but allow a few exceptions?

Question

For my father's PC (who is a senior citizen), I would like to generically block Firefox from remembering passwords. However I would like it to remember the password for a few select websites (Yahoo Mail, Facebook, NYTimes). Is this possible?
You seem to be ale to generically allow Firefox to remember passwords and block certain websites. But not vice-versa.
I've tried going to: "about:permissions" but if you change the Default Permissions for All Pages to Block for Store Passwords, then that also blocks passwords for any individual entries

Answer 1

You will have to toggle the Password Manager on/off to have Firefox save or fill names and passwords.
Only if the Password Manager is enabled then you can use it.
Maybe it is an idea to hide the notification icon and the popup (or only the popup) on the Navigation Toolbar, so that Firefox won't offer to remember passwords.
Add code to the <b>userChrome.css</b> file below the default @namespace line.
*http://kb.mozillazine.org/userChrome.css
<pre><nowiki>@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"); /* only needed once */
#password-notification-icon { display: none !important; }
#notification-popup[popupid="password-save"] { display: none !important; }
</nowiki></pre>
The customization files userChrome.css (user interface) and userContent.css (websites) are located in the <b>chrome</b> folder in the Firefox profile folder.
*http://kb.mozillazine.org/Editing_configuration
* Create the chrome folder (lowercase) in the <xxxxxxxx>.default profile folder if this folder doesn't exist
* Use a plain text editor like Notepad to create a (new) userChrome.css file in this folder (the names are case sensitive)
* Paste the code in the userChrome.css file in the editor window and make sure that the userChrome.css file starts with the default @namespace line
* Make sure that you select "All files" and not "Text files" when you save the file via "Save file as" in the text editor as userChrome.css. Otherwise Windows may add a hidden .txt file extension and you end up with a not working userChrome.css.txt file
You can use this button to go to the currently used Firefox profile folder:
*Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
*http://kb.mozillazine.org/Profile_folder_-_Firefox