Unexplained warning on HTTP

I’ve just installed Nagios and before I go trying to monitor beyond the localhost, I need to resolve a local problem. HTTP is coming up with a warning HTTP WARNING: HTTP/1.1 403 Forbidden. I can manage Nagios via the web interface from another host and I can access the Apache test page from another host. Seems to me that HTTP is just fine. Am I looking at this wrong?

Thanks

Problem solved. The issue was with the default apache test page. Creating /var/www/html/index.html solved the problem.