how config microtik by winbox to limit some user to only access to open only some site
http://wiki.mikrotik.com/wiki/Manual:IP/Firewall
Your question is too vague to give a specific answer. You may want to read up on firewall configuration, traffic control and related topics then ask about the parts that you didn’t understand.
i think you can use walled garden in ip hotspot
and allow some users to access a web site without login