Because the Cisco IOS Firewall uses Cisco IOS access control lists (ACLs) as the first line of defense on packets entering the router, if logging is enabled on an interface ACL entry that is permitting packets to get to the firewall, you may see that a packet is logged as being allowed. This log message can be ignored and for the disposition of the packet by the firewall, you should look for a subsequent log message displayed by the firewall.
To see the packets that are dropped by the firewall, the ip inspect log drop-pkt command must be enabled.
This URL should help you:
http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_guide09186a008028b448.html
