For trouble shooting purposes you may want to turn on some logging options. If you uncheck “Log info to file” option, logging will be completely turned of. Most useful logging options are “Database / ODBC” and “Other Errors”. These arrors are not supposed to happen and keeping the log option for these may improve usability / serviceability. If you wish to see who is trying to access your server and who is granted or denied access, then you can choose to log successful and failed user login attempts. Logging the other “activity” is mostly for debugging purposes and you should not need it most of the time. Remember that turning on log reduces performance considerably. Having the log turned on for errors should be fine since such errors are assumed to be infrequent.
The log file needs to be located in a directory where IIS has write access permissions. The log file name can be left blank, in which case logging will be turned off.