I would like to publish my internal web server to internet
plz help…
Here is my network diagram

http://wiki.mikrotik.com/wiki/Manual:IP/Firewall/NAT#Port_mapping
Forward port tcp/80.
You will also have to port fortward port 80 from your dsl modem to the wan interface of the mikrotik. If your modem has DMZ just put the 192.168.1.254 ip there so you only have to deal with port forwarding on the mikrotik from now on. Or better yet, change your dsl modem to bridge mode and add a pppoe client interface to the wan interface of the mikrotik.