From Lifehacker:
... reader David has a simple solution.
1. In Firefox's URL bar, type in: about:config and agree to the pop-up message.
2. Search for: browser.urlbar.trimURLs.
3. Double-click or right-click and select "toggle" to change the value to false.
Now you'll get the full HTTPS or HTTP in the URL so you won't be confused on whether you're viewing a secure site.
