xorg.conf

http://en.wikipedia.org/wiki/Xorg.conf
http://www.x.org/archive/X11R6.8.0/doc/xorg.conf.5.html


Section "Device"
Identifier "Configured Video Device"
Driver "vesa"
EndSection

Section "Monitor"
Identifier "Configured Monitor"
EndSection

Section "Screen"
Identifier "Default Screen"
Monitor "Configured Monitor"
Device "Configured Video Device"
EndSection

Section "ServerLayout"
Identifier "Default Layout"
Screen "Default Screen"
EndSection

Kind of hierarchy structure in different sections. Each section has the Identifier can be used as name. Other section can further use the name in its own place. For the example above:
ServerLayout -> Screen -> Monitor&Device

When testing, you can find log in /var/log/Xorg.0. The log is prefix with Markers meaning:
Markers: (--) probed, (**) from config file, (==) default setting,
(++) from command line, (!!) notice, (II) informational,
(WW) warning, (EE) error, (NI) not implemented, (??) unknown.