In simple terms, it means that there was some "Internal Server Error" while processing your request. You need to study carefully the trace at the server window to find out more about the error.

These errors can occur while translating your jsp source to a servlet. These are translation-time errors and occur mostly because of some syntax error in the jsp file or in the generated java file. Please use the error-message at the server-window for debugging.

Errors can also occur at request-time. Again, the information about specific problem/exception can be obtained by looking at the server-side trace.