Error-message numbers have four digits; the first one or two of those digits identify the message category. The message-number prefixes and the categories they identify are defined as follows:
| Prefix | Error |
| 1 | Problems with files used to build the help file |
| 2 | Problems with the project file |
| 30–31 | Problems with build tags or build-tag expressions |
| 35–36 | Problems with Help macros |
| 40–41 | Problems with context strings |
| 42–45 | Problems with footnotes |
| 46–47 | Problems with the topic file |
| 5 | Other problems |