you need to set forum permissions lol
go to ur admincp > Forums & Moderators > Forum Permissions
and in there edit UserGroup : > Unregistered / Not Logged In for any one forum
and then using User Group-Based Permission Duplicator , copy them to all forums
what permissions you will set there : -
Edit Unregistered / Not Logged uroup
then there Set All to No
just set yes the first one Can View Forum,
if you want the guests to see the threads
this will make guests not to posts posts in any section
More info see this doc : -
HTML Code:
http://www.vbulletin.com/docs/html/forums_moderators