The padlock has been replaced by the site identity button, for details on using it see https://support.mozilla.com/kb/Site+Identity+Button

You can get the drop down list by either right-clicking on the back/forward buttons, or holding down the left button until the list appears.

If you want the drop-down arrow you can add it with the Back/forward dropmarker add-on - https://addons.mozilla.org/firefox/addon/backforward-dropmarker

If you are still not satisfied, you may downgrade using the steps given here http://malektips.com/firefox_0039.html

In Firefox 4 you no longer have the Status bar that showed the padlock in previous Firefox versions.
The padlock only shows that there is a secure connection and doesn't guarantee that you are connected to the right server.
So you might still be connected to the wrong server if you make a typo in the URL and someone has claimed that mistyped URL.
The functionality of the padlock has been replaced by the How do I tell if my connection to a website is secure? on the left end of the location bar.

See also:

• http://www.dria.org/wordpress/archives/2008/05/06/635/

You can click the How do I tell if my connection to a website is secure? on the left end of the location bar to see the padlock if there is a secure connection.

A click on the "More Information" button will show more details about the connection.

The background color of the "Site Identity Button" on the left end of the location bar will change color (blue or green) and show the domain in case of a secure HTTPS connection.

• Hover the How do I tell if my connection to a website is secure? then to see "Verified by xxxx"
• Click the "Site Identity Button" on the left end of the location bar to see the padlock
• Click the "More Information" button in that pop-up to see additional information about the connection.

You can use this extension to get a padlock on the location bar.

• Padlock: https://addons.mozilla.org/firefox/addon/padlock-icon/