I tried to access a file on my site that I know does not exist. Why did Apache log a 200 OK?
123.456.789.123 - - [1/Jan/1070:00:00:00 +0000] "GET /file_i_know_isnt_real.php HTTP/1.1" 200 38104 "-" "Mosaic/0.9"
The Apache Foundation has determined that 404's are not concerning enough on production servers to warrant logging, as they are rather common and would otherwise fill the error log.
More information on why this is can be found in the original Apache bug report that resulted in this behavior.
The 200 OK that is logged is stating that the Error Document was successfully rendered.
The Apache LogLevel can be configured to display "info" reports. This can be changed via WHM > Apache Configuration > Global Configuration.