I recently discovered this list of reason codes, their explanation and in some cases the HTTP code that is returned for IIS6’s httperr log files. Httperr log files are new to IIS6, are usually stored in c:\windows\system32\logfiles\ directory and contain interesting information you don’t see in your regular IIS log files. As the name suggests they only contain “error” information (not information about every single request), and are more low-level. For example if a site is disabled, or if the app-pool is recycled then that information gets logged there. The reason phrases can be a little cryptic, although the “decoder ring” I liked to above helps. I can’t seem to get this working on XP SP2 tho….