I noticed you asked about Allstate before: why is allstate.com not a secure website. Are you still getting the gray exclamation triangle on that site? Are there particular pages where you notice the problem? Feel free to post more specific addresses since otherwise we may not see what you're seeing.

On Staples, it seems that most pages are not designed to be accessed using HTTPS -- when I try HTTPS it redirects to HTTP and shows the globe icon.

However, the login page definitely should give you a gray lock:

https://login.staples.com/easylogin/logon

If you get the triangle, try using Ctrl+Shift+r to reload the page and the various assets linked into the page (scripts, style sheets, images). Does it change to a lock? Sometimes Firefox shows the triangle instead of the lock when it uses cached images on a page that was visited very recently. This issue has been known for a while so hopefully it will get fixed.

By the way, I get a green lock on Allstate (screen shot attached).

Sometimes add-ons can cause a mixed content warning, particularly those that inject advertising into pages. Could you test in Firefox's Safe Mode? That's a standard diagnostic tool to deactivate extensions and some advanced features of Firefox. More info: Diagnose Firefox issues using Troubleshoot Mode.

If Firefox is not running: Hold down the Shift key when starting Firefox.

If Firefox is running: You can restart Firefox in Safe Mode using either:

• "3-bar" menu button > "?" button > Restart with Add-ons Disabled
• Help menu > Restart with Add-ons Disabled

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any improvement?