The Attorney General said he was publishing legal guidance notes previously only issued to the media to "help stop people from inadvertently breaking the law."
Dominic Grieve QC said: "Blogs and social media sites like Twitter and Facebook mean that individuals can now reach thousands of people with a single tweet or post. This is an exciting prospect, but it can pose certain challenges to the criminal justice system.
"In days gone by, it was only the mainstream media that had the opportunity to bring information relating to a court case to such a large group of people that it could put a court case at risk.
"That is no longer the case and is why I have decided to publish the advisories that I have previously only issued to the media.
"This is not about telling people what they can or cannot talk about on social media - quite the opposite in fact, it's designed to help facilitate commentary in a lawful way.
"I hope that by making this information available to the public at large, we can help stop people from inadvertently breaking the law, and make sure that cases are tried on the evidence, not what people have found online."