Nagios Support Forum

I know there are only basic features for Nagios in monitoring website, but ...

1. When using "Website Monitoring Wizard" or "Website URL Monitoring Wizard" to monitor HTTP website, what is the "basic monitor" indicate and how deep it work? can it's parameter be changed? (e.g. Nagios probe website status, but website is busy and not reply in time, what will Nagios do?)

2. When browsing websites, the HTTP status codes(or HTML error codes e.g. 404/500) can tell us if website goes wrong, can Nagios monitor and alert?

The check_http plugin is extremely flexible. I would run some test from the command-line and see what options suit your needs.
The above will give you the full options of this plugin (there are many).