hello it depends if the information is stored as form data or password - please see Control whether Firefox automatically fills in forms & Password manager - Remember, delete, change and import saved passwords in Firefox.

please also Update Firefox to the latest release since you're using an outdated version with known security vulnerabilities.

Use these steps to remove saved (form) data from a drop down list:

1. Click the (empty) input field on the web page to open the drop down list
2. Highlight an entry in the drop down list
3. Press the Delete key (on Mac: Shift+Delete) to remove it.

• http://kb.mozillazine.org/Deleting_autocomplete_entries

DELETING EMAIL ADDRESS FROM LOGIN FORM OR TEXT FIELD:

I had the same problem. It took me an hour to figure this out. I didn't understand the response you previously received. The following are instructions on how to solve this problem. I have Windows 7 Professional and the latest Firefox. Details may vary depending on your browser and operating system.

In my Firefox browser, I went to Tools, then Options, then the "Privacy" tab. In the "Privacy" tab, go to the "History" section. There is an option to "Clear history when Firefox closes" with an option to check or uncheck this box (My box was checked) Click on the "Settings" button NEXT to this line.

[If this button is not available, you may have to uncheck the "Always use private browsing mode" box above in this same "History" section]

A "Settings to Clearing History" window will pop up. Check the "Cookies" and "Form & Search History" boxes so that Firefox clears these when you quit your browser. Click OK, then get out of your browser. Open up Firefox again and your email address should be gone.

I don't know whether checking the "Cookies" box or "Form & Search History" box solved the problem. I checked both boxes.

You can go back and uncheck the "Cookies" and "Form & Search History" boxes so that Firefox remembers your email address again.

right click on the wrong address (the one you want to delete) and hit delete on your keyboard. It worked for me.