Whenever you see an exit status
code other than zero returned, 255 in above case, it means that part failed.
Try run that bit of code next time your experiencing issues, it will give you some more details to look for:
sudo /usr/sbin/lighttpd -tt -f /etc/lighttpd/lighttpd.conf
pi@ph5b:~ $ man lighttpd
[..]
-f configfile
Load configuration file configfile.
[..]
-tt Test the configuration file for syntax errors, load and
initialize modules, and exit.
EDIT:
pi@ph5b:~ $ sudo /usr/sbin/lighttpd -tt -f /etc/lighttpd/lighttpd.conf; echo $?
0