You may have face this error.
Solution is install libidn-devel with yum.
kasun@kasendra skipfish-2.05b$ make
cc -L/usr/local/lib/ -L/opt/local/lib skipfish.c -o skipfish -O3 -Wno-format -Wall -funsigned-char -g
-ggdb -I/usr/local/include/ -I/opt/local/include/ -DVERSION=\"2.05b\" \
http_client.c database.c crawler.c analysis.c report.c -lcrypto -lssl -lidn -lz
skipfish.c: In function ‘main’:
skipfish.c:245:54: warning: variable ‘has_fake’ set but not used [-Wunused-but-set-variable]
http_client.c:39:18: fatal error: idna.h: No such file or directory
compilation terminated.
make: *** [skipfish] Error 1
kasun@kasendra skipfish-2.05b$
Solution is install libidn-devel with yum.