Default page hideing

Hy!
I have a big question!
How i can hide the default page of the router? Or how i can change, the default 80 port to an another..
I don’t want to my clients can access the login page tipping the simple ip address of the router…

And it is possible to create a user, to see only the restart function of router?

Thank’s for help!

/ip service set www port=

and see http://wiki.mikrotik.com/wiki/Router_AAA#User_Groups