If you can rule out malware/spyware on your PC, then the remaining risks are small.

Usually web site #1 cannot access information you have open from web site #2 in a different tab or window. However:

Some legitimate sites use another site's API to access information about you (e.g., Facebook profile information). This usually requires your approval, although the disclosure that you are sharing information isn't always obvious. I don't know whether there is any way to get GMail messages or your GMail address book.

Malicious web sites sometimes contain tricky scripts designed to siphon information and Firefox is regularly updated to shut these down as they are reported to Mozilla. There is an inevitable window of vulnerability (which can vary from hours to months) between the time an attack is developed and when browsers are updated.

I'm sure this isn't as definitive answer as you would like, but that's what comes to mind.

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I assume you have logged out of GMail so the session active at that time was closed. It also wouldn't hurt to verify your recovery email address and change your password.

clear it and please open the face book. its showing untrusted connection