if you are speaking of certificate issues, you'll need to contact earthlink about problems, Firefox can't do anything about them. What do you want here?

Could you check the error page for two details:

(1) What server is said to be insecure? This may be a real website, or it might be a bulk mail vendor's site.

(2) Is there a code in ALL_CAPS on the error page? You might need to click an Advanced button to access the code.

If the error is not from Firefox itself, for example, it is from your security software, does it give more information about the insecure address?