Credit cor-el: In Firefox 4 and later 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 The functionality of the padlock has been replaced by the Site Identity Button on the left end of the location bar.

See also:

   http://www.dria.org/wordpress/archives/2008/05/06/635/
   https://support.mozilla.com/kb/Site+Identity+Button
   http://www.mozilla.com/en-US/firefox/security/identity/ 

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

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

Andy, Thanks for the info. It was a bit of a shock not seeing the old icon. The new system will take a bit to get used to.

Again thanks for the quick reply and links, they were very helpful in explaining what had changed.

-Charlie