I think Firefox would only display the Master Password dialog if you had already saved your login for the site. To DELETE a saved login for the site, please try here:

• Windows: "3-bar" menu button (or Tools menu) > Options
• Mac: "3-bar" menu button (or Firefox menu) > Preferences
• Linux: "3-bar" menu button (or Edit menu) > Preferences
• Anyone: type or paste about:preferences in the address bar and press Enter/Return

In the left column, click Security. Then on the right side, find the "Saved Logins" button. You may need to enter your Master Password to interact with this dialog (you definitely need to enter it to view the actual passwords associated with the saved logins).

Does that help?

The login information is no longer listed in my saved passwords and hasn't been since a recent admin update (when I tried to log in after the update, I found that the "save" was no longer in my password manage)--that was the first thing I checked.

That is why I am surprised that the master password prompt keeps showing up, since the login/password info is not even saved anywhere, although it once was before the administrators for the site did their recent update. I am surprised that the previously saved login info was apparently automatically deleted as a result of the admin update. I am reconciled to not having that "saved password" convenience anymore, but now I just want to get rid of the annoying master password prompts since they are now moot.

I thought maybe if I listed the site as an "exception" that might fix it, but that idea is a shot in the dark...either way I still want to know how to list an exception, because that window is completely grayed out.

Thanks for the response though. If anyone has any ideas, please advise...

Okay, this is not going to be suitable for many users, but since I didn't find an add-on for it, this is what I've come up with so far. Maybe someone can simplify it.

Overview

1. Change a preference so you can run privileged commands in the Browser Console (the kinds of command that Firefox and extensions can run, but web pages cannot run)
2. Open the Browser Console and execute a script
3. Verify that the exception has been added
4. For safety, disable the change in #1

(1) Enable Chrome Debugging

(A) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(B) In the search box above the list, type or paste devt and pause while the list is filtered

(C) Double-click the devtools.chrome.enabled preference to switch the value from false to true

Keep this tab open for step #4

(2) Add the Exception

Select and copy the following script:

var loginManager = Components.classes["@mozilla.org/login-manager;1"]
 .getService(Components.interfaces.nsILoginManager);
loginManager.setLoginSavingEnabled("https://www.example.com/", false);
loginManager = "";

Open Firefox's Browser Console using either:

• Ctrl+Shift+j
• "3-bar" menu button > Developer > Browser Console
• (menu bar) Tools > Web Developer > Browser Console

There should be a command line at the bottom. Paste the script and edit the host name from www.example.com to the actual site you want to block. Then press Enter to run the script. It may display a void or "" return value. If you got an error, check to make sure the " wasn't lost at the end of the host name.

(3) Confirm the Addition

On the Options/Preferences page, Security panel, click the Exceptions button to confirm that the host name now appears there. If all is well, you're done with the Browser Console and you can close it.

(4) Disable Chrome Debugging

In about:config, double-click the devtools.chrome.enabled preference to switch the value from true to false

You're done with about:config and you can close it.

You may have to start typing the first letters of the username to open the drop-down list.

See also:

• Saved Password Editor: https://addons.mozilla.org/firefox/addon/saved-password-editor/