http server error 404

[kokoro]

I cannot browse my thttpd web server (tutorial macsat)
just a index.htm, and also rrd tool the same:
i have the error "404 file not found" displayed by the web server.

Where is the bug?
Here are the processes, if something else is needed please ask

PID Uid VmSize Stat Command
1 admin 372 S /sbin/init
2 admin SW [keventd]
3 admin SWN [ksoftirqd_CPU0]
4 admin SW [kswapd]
5 admin SW [bdflush]
6 admin SW [kupdated]
7 admin SW [mtdblockd]
39 admin 148 S telnetd
44 admin 288 S httpd eth1
47 admin 224 S klogd
51 nobody 332 S dnsmasq
52 admin 244 S syslogd -m 0 -O /tmp/syslog.log -S -l 7
54 admin 368 S nas /tmp/nas.lan.conf /tmp/nas.lan.pid lan
57 admin SW [khubd]
67 admin 168 S lpd
69 admin 164 S p9100d -f /dev/usb/lp0 0
71 admin 164 S p9101d -f /dev/printers/0 1
74 admin 192 S waveservermain
76 admin 200 S rcamdmain
80 admin SW [usb-storage-0]
81 admin SW [scsi_eh_0]
86 admin 208 S infosvr br0
87 admin 440 S watchdog
90 admin 244 S ntp
97 admin SW [kjournald]
111 admin 284 S /opt/sbin/cron
135 admin 236 S udhcpc -i eth1 -p /var/run/udhcpc0.pid -s /tmp/udhcpc
141 nobody 2396 S /opt/sbin/thttpd -C /opt/etc/thttpd.conf
144 admin 312 S /usr/sbin/smbd -D -l /opt/var/log/smbd.log -s /opt/et
148 admin 760 S /usr/sbin/nmbd -D -l /opt/var/log/nmbd.log -s /opt/et
151 admin 260 S dropbear
153 admin 404 S stupid-ftpd
160 admin 496 S upnp -D -L br0 -W eth1
162 admin 704 S dropbear
163 admin 528 S -sh
166 admin 392 R ps

[samoht]

On which port is thttpd running and what address and port did you call up?

[kokoro]

Macsat tutorial: http://www.macsat.com/php_web.php

[ip router]:81/index.htm
[ip router]:81/wiviz/wiviz.html

:80 same error

By the way, how router can differenciate with web interface configuration:
[ip router] or [ip router]/index.php ? only port 80 instead of 81 ?

thx