In Windows Help version 3.0, error messages included the prefixes P and R to indicate whether the error occurred in the topic file or in the Help project file. In Help version 3.1, theses prefixes have been replaced by a numbering scheme that differentiates build errors into eight categories.
Error message numbers have four digits. The first one or two digits identify the message category. The third and fourth digits establish the message order within the category. The message number prefixes and the categories they identify are listed in the following table.
| Prefix | Error category |
| 1 | Problems with files used to build the Help file |
| 2 | Problems with the Help 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 topic footnotes |
| 46–47 | Problems with RTF topic files |
| 5 | Other problems |
You might encounter errors other than the build errors described here. For more information, see the README.TXT file.