I'm gona re-design my forum , but i wanna set an index for my forum so others to show that
we're under construction and i can design my forum without showing index for me , only for
others ?

you can turn off your forum - set it offline through forum settings
admin panel >> configuration >> settings >> Board Online / Offline >> Board Closed --> yes
Yes, but i don't wanna show my forum totally, i just wanna hide it , i know offline method by Board On/Offline.
But it exist any way to do via index ?
^ along with that you can put a index.html / construction.html page and divert others to it through
.htaccess (
eg.)
Thread can be closed .
I solved this problem by creating new index renaming comingsoon.html and then went to .htaccess to my root
and added there in the top some texts and now it's fine ,
Thanks you also .m.