Download the plugin: http://get-simple.info/extend/plugin/display-error/864/
With this plugin you can see from admin > support:
- the error log of getsimple, delete errors or delete log file full.
- it shows 404 error too. The plugin uses a frontend-hook: error-404; if there is a error 404 then the log for errors 404 is created for the plugin. The 404 error can be summarized.
The errros can be deleted individually or completely.
The plugin use the database of http://cleantalk.org/ to know if it's spam.
1) Activate the plugin from admin > plugins.
2) From admin > support you can view errors.
If you can any question you can do in Forum Thread: http://get-simple.info/forums/showthread.php?tid=5791&pid=43829#pid43829 ; or here in this web.