In most distributions this means that the system is booting by default into runlevel 5, which is supposed to respawn (re-start again after it's been exited) a graphical login via xdm, kdm, gdm, or whatever, and the system can't locate the program.
However, "Id" can also indicate the absence or misconfiguration of another program, like mingetty, if init tries to respawn itself more than 10 times in 2 minutes.
Id "x" is the number in the leftmost column of the /etc/inittab file:
# Run gettys in standard runlevels
Commenting the offending line out and then fixing the errant program and testing on the command line will allow you to see any error messages that go to standard error output (console) if the errors are not going to the system log file. Uncomment the line and restart init with "kill -SIGHUP 1" or "telinit q" to cause init to reinitialize and reread the /etc/inittab file.
Some systems, however, rewrite /etc/inittab when booting. In that case, refer to the init man page, and/or the settings in /etc/sysconfig/init.
Refer to the init and /etc/inittab man pages for detailed information.