If you have any doubts about the extent of the judge's admonishment, you should tell the judge you have a question about it.
This answer is for general education purposes only. It does not create an attorney-client relationship nor is it intended to provide legal advice. The answer is based on the limited information provided and the answer might be different had additional information been provided. You should consult an attorney.
What are you posting, if not about the case? Are you asking if you can post on your facebook account that you are on jury duty and your case is expected to last several days? Almost certainly. Are you posting on facebook that you are on jury duty and the plaintiff/defendant/accused/attorney/judge/bailiff is an idiot (or something good)? Perhaps not. Ask the judge if you have a question as to what is allowed.
This information is provided for general informational purposes and is not intended as legal advice. An attorney licensed in your jurisdiction can answer questions specific to your specific fact situation and provide you appropriate advice as necessary based on the specific facts of your matter and the jurisdiction in which you reside. If you are in Arizona and interested in discussing your matter further I can be reached at: (480) 838-9000 Mark D. Fullerton, P.C. 1839 S. Alma School Road, Suite 275 Mesa, Arizona 85210