Version - cups-1.4* and above 

If i modify any of the option in cups.conf  and make spell mistake, it complains in error_log. However, this doesn't seems to validating option "ErrorPolicy" we added sometime back (default releases in RH-6 and after 1.3.7 rebase in RH-5)

Steps to reproduce this... 

1)
[root@dhcp233-34 ~]# grep Max /etc/cups/cupsd.conf
MaxLogSize   <---------- Remove size
[root@dhcp233-34 ~]#

[root@dhcp233-34 ~]# /etc/init.d/cups restart
Stopping cups:                                             [  OK  ]
Starting cups:
[root@dhcp233-34 ~]#                                        [  OK  ]
[root@dhcp233-34 ~]# cat /var/log/cups/error_log
E [25/Feb/2015:18:10:59 +0530] Missing integer value for MaxLogSize on line 1! <------ Complains integer missing

2)

[root@dhcp233-34 ~]# grep LogLevel  /etc/cups/cupsd.conf
LogLevel rn <------- made spell mistake in LogLevel
[root@dhcp233-34 ~]#

[root@dhcp233-34 ~]# cat /var/log/cups/error_log
E [25/Feb/2015:18:10:59 +0530] Missing integer value for MaxLogSize on line 1!
W [25/Feb/2015:18:11:57 +0530] Unknown LogLevel rn on line 11. <---------------  Complain for unknown level
[root@dhcp233-34 ~]#

[root@dhcp233-34 ~]# grep Error  /etc/cups/cupsd.conf
ErrorPolicy test <----------Error policy is invalid but it doesn't complain anything.
[root@dhcp233-34 ~]#

[root@dhcp233-34 ~]# cat /var/log/cups/error_log
E [25/Feb/2015:18:10:59 +0530] Missing integer value for MaxLogSize on line 1!
W [25/Feb/2015:18:11:57 +0530] Unknown LogLevel rn on line 11.
[root@dhcp233-34 ~]#

 ^^ no such commented by cups in error_log for invalid entry.