Syslog categorizes its messages by facility. Facilities are system-named buckets for reporting syslog messages. Supported facilities on most Linux/Unix systems are:
auth For many security events
auth-priv For access control related messages
cron Events that occur during cron jobs
daemon For system processes and daemons
kern For kernel messages
lpr For printer and printing related messages
mail For mail handling messages
mark Messages generated by syslog itself
news Messages having to do with the news service
syslog More messages generated by syslog
User The default facility when none is defined
Uucp For logging uucp related messages
local(0-7) Miscellaneous default services
Unlike facilities, priorities are hierarchical levels designed to indicate the urgency of the message being logged. The following is a list of priorities listed by urgency:
Debug Debug information, for debugging software
Info Just thought you might like to know
Notice Something that should be noted
Warning Something bad may have or could happen
Err Something bad happened
Crit Something really bad happened
Alert Hey! Something bad is happening! Call the cell phone!
Emerg Quick, pull the plug, shut down the Internet!
Syslog comes preconfigured on most distributions of Linux including my fresh Ubuntu install. The default location for log files is located at /var/log.
JavaScript 
Building a Secure Web Server
