centos系统下无法启动httpd

[root@csit yang]# service httpd start
Starting httpd:                                            [FAILED]

[root@csit httpd]# cd /etc/httpd/conf.d/

[root@csit conf.d]$ grep NSSEngine *
nss.conf:NSSEngine on

[root@csit conf.d]$ vi  nss.conf 
#   SSL Engine Switch:
#   Enable/Disable SSL for this virtual host.
#NSSEngine on

[root@csit httpd]# service httpd restart
Stopping httpd:                                            [  OK  ]
Starting httpd:                                              [  OK  ]