[Error Message] error after install

[thewanderer]

Hi can anyone plz help me with this error i have installed mybb on my site it has let me install when i go to admin page and put in login info and click enter i get this

Forbidden
You don't have permission to access /test1/admin/index.php on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

[.m.]

check whether admin folder & index.php file physically exist

check whether they are accessible - folder should have CHMOD 755
& index.php file can have CHMOD 644 (or higher 646 / 664 / 666)

[thewanderer]

yip all there and all chmod ok

[.m.]

can you check if mod_security is affecting or if rewrite rules are affecting
if you are not sure about mod_security then please contact your web host