If you receive a subpoena to appear in court DO NOT IGNORE IT. YOU MUST APPEAR AT THE INDICATED TIME AND LOCATION.
A subpoena is a command for you to appear and testify on behalf of either the State (Prosecution) or the Defendant. Even if you believe you have no relevant testimony or factual knowledge of the case, you cannot be relieved from your attendance in court other than by the Judge who is presiding over the matter.
For more information, look at the subpoena for the size and color and compare it to one of the specimen subpoenas below: The name of the person who subpoenaed you should appear at the bottom of your subpoena.
Click on the image for a closer view of the subpoena in Adobe (pdf) format.