How to prevent posting?

How to prevent a separate user to post on the forum without ban?

Only thing I can think of is create a special user group for him that is hidden and change all the permissions.

One small help more ... where to setup write premission for that group ?

you do it in the forum permissions General=> Categories and Forums

Yeah it is a bit of a pain in the ass if you have a lot of categories and topics.

CharlieFSA this is kind of a odd question coming from you.
Meaning you have been a member here for a wile and have your forum or forums for a wile.

but anyway like blindbat said.. you would put the person in a separate group.
i would make hidden and no color and a closed group so the member would not even know they where in there own specific group.

then you have to set the permissions as you want for the forums.

you will have to do them one at a time.. but to make things a lil fatser.
select group permissions option for the member/group you created. then set on forum with the permissions as you want them and go through the list and just select copy permissions from the previous forum.

Now keep in mind you will only do that if you want them to have the same permissions for every forum.. if not then you will have to do them one at a time..

once again be sure to create the group as hidden closed and add no color.