Step 1.

Type in about:config into the URL bar in your FireFox browser and press enter.

Step 2.

Scroll down until you see the following option in the list:
"signed.applets.codebase_principal_support"

Double click that option and it will turn bold indicating that it is now on.

Step 3.

Go back to your HTML editing control and refresh the screen. A popup security dialog window will appear. Select the "Remember this decision" option and click "Allow".

Step 4.

Close all your FireFox browser windows and restart the browser.

You're HTML control should now have all the options enabled in FireFox.