Hello,
I have successfully installed nagios and pluings but having difficulty in it's configuration:
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root@server [/usr/local/nagios/etc]# ../bin/nagios -v nagios.cfg

Nagios 1.2
Copyright (c) 1999-2004 Ethan Galstad (nagios@nagios.org)
Last Modified: 02-02-2004
License: GPL

Reading configuration data...

Running pre-flight check on configuration data...

Checking services...
Checked 38 services.
Checking hosts...
Checked 15 hosts.
Checking host groups...
Checked 6 host groups.
Checking contacts...
Checked 2 contacts.
Checking contact groups...
Checked 6 contact groups.
Checking service escalations...
Checked 2 service escalations.
Checking host group escalations...
Checked 2 host group escalations.
Checking service dependencies...
Error: Dependent service specified in service dependency for service 'Website #2' on host 'nt1' is not defined anywhere!
Error: Service specified in service dependency for service 'Website #2' on host 'nt1' is not defined anywhere!
Error: Service dependency definition for service 'Website #2' on host 'nt1' is circular (it depends on itself)!
Error: Dependent service specified in service dependency for service 'Website #2' on host 'nt1' is not defined anywhere!
Error: Service specified in service dependency for service 'Website #2' on host 'nt1' is not defined anywhere!
Error: Service dependency definition for service 'Website #2' on host 'nt1' is circular (it depends on itself)!
Error: Dependent service specified in service dependency for service 'Website #1' on host 'nt1' is not defined anywhere!
Error: Service specified in service dependency for service 'Website #1' on host 'nt1' is not defined anywhere!
Error: Service dependency definition for service 'Website #1' on host 'nt1' is circular (it depends on itself)!
Error: Dependent service specified in service dependency for service 'Website #1' on host 'nt1' is not defined anywhere!
Error: Service specified in service dependency for service 'Website #1' on host 'nt1' is not defined anywhere!
Error: Service dependency definition for service 'Website #1' on host 'nt1' is circular (it depends on itself)!
Checked 4 service dependencies.
Checking host escalations...
Checked 0 host escalations.
Checking host dependencies...
Checked 0 host dependencies.
Checking commands...
Checked 22 commands.
Checking time periods...
Checked 4 time periods.
Checking for circular paths between hosts...
Checking for circular service execution dependencies...
Checking global event handlers...
Checking obsessive compulsive service processor command...
Checking misc settings...

Total Warnings: 0
Total Errors: 12

***> One or more problems was encountered while running the pre-flight check...

Check your configuration file(s) to ensure that they contain valid
directives and data defintions. If you are upgrading from a previous
version of Nagios, you should be aware that some variables/definitions
may have been removed or modified in this version. Make sure to read
the HTML documentation on the main and host config files, as well as the
'Whats New' section to find out what has changed.
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How should I proceeed with this?
Thank you

I am having the same issue

I also couldn't run make install-init
i get this error:

[nagios@localhost nagios-1.2]$ make install-init
/usr/bin/install -c -m 755 -d -o root -g root /etc/rc.d/init.d
/usr/bin/install: cannot change permissions of `/etc/rc.d/init.d': Operation not permitted
make: *** [install-daemoninit] Error 1
[nagios@localhost nagios-1.2]$

It looks to me like you still have the sample dependencies configured in the dependencies.cfg file. You can either remove all the entries in that file or comment them out by placing a # in the beginning of each line or you can go into the nagios.cfg file and comment out this line cfg_file=/usr/local/nagios/etc/dependencies.cfg. This will tell nagios to ignore the contects of the dependencies config file. Hope this helps.