what is the best way to monitor user activity on web?
how to get the bandwidth usage report?
by user activity you mean you wanna see what website did your user opened or how much your user download and upload?
We need more info, be more specific. For example, if you use hotspot on your mtik’s, you can view complete amount of data uploads/downloads by clicking on users queue or you can use torch tool for more specific view on data flow.
i want to see that which websites are accessed by users. also i want to generate the bandwidth usage report of each
user, i have not set up a hotspot.
If you wanna see what website did your user accessed:
first of all you should enable your webproxy and make transparent proxy. really easy. just follow instruction in link below:
http://wiki.mikrotik.com/wiki/Manual:IP/Proxy#Proxy_configuration_example
if you are done with your web proxy so you should make Sys log server in order to see what webpage are accessed.
so in your router:
/System logging action add name=syslog target=remote
/System logging add action=syslog topics=web-proxy
Then in Winbox, go to:
System → Logging → Action
open syslog and you should set parameter. it’s easy.
if you’re looking for free software for Windows, so Dude is a good idea 
http://wiki.mikrotik.com/wiki/Manual:The_Dude/Syslog
and if you wanna manage your bandwidth you may run Hotspot or PPP. I think it’s easier for you to set Hotspot. and should not that I don’t know how many computers are running in your network, maybe if you give me more detail it would be easier to help.
for setting Hotspot:
http://wiki.mikrotik.com/wiki/Manual:Hotspot_Introduction
I hope this is easy enough
i have forwarded my 80 port of my live ip to my local server . so how can i set up web proxy. i know about dude but is there any free windows software to monitor logs which generate the graphical reports.
I don’t know any other free software. you should pay for rest of them
i have forwarded 80 port to local server . so how can i forward it to web proxy. can i forward one single port to multiple ports.?
the best application I use for tracking web proxy requests is “Kiwi Syslog Daemon” it is not free but you can find cracks for it online.
I have a log files for all my users make online through the last 4 years. 
by the way tushar123 activating the web proxy is very simple just redirect all the traffic coming on port tcp 80 to for example 8080 (through your firewall nat) then enable your mikrotik web proxy make it lessen to port 8080 (ip/web proxy)
But i have forwarded tcp 80 port to my server to access my server outside the network. so can i forward the 80 port to
sys log server .
can i forward one port to multiple ports.
You don’t forward port 80 to the syslog server.
You forward port 80 to the web proxy mikrotik on port 8080.
If you’re running proxy in the same router, use action=redirect, to-ports=8080
redirect = steal the connection yourself.
Web proxy will then do its job, going to the net, collecting pages, pictures, etc, and then forwarding back to the client computers transparently. Meanwhile - for each request that it proxies, it will generate a logging event.
Hossain’s instructions tell you how to configure the Mikrotik to send these log events to a remote syslog server for permanent storage.
If you want to turn those into graphs, you’ll need some other software that can read the syslog output, and generate whatever reports you want. I have no idea about what programs are available for this task.