[RonHiler]

Ah, sorry 'bout that. I forgot to mention about prefixes. Tnguy3n is correct, you have to substitute your own database prefix (if any). My prefix for my database tables is "vb_". If you don't use a prefix, change these lines as follows:
$result = mysql_query("SELECT postid FROM vb_post WHERE visible=1");
to
$result = mysql_query("SELECT postid FROM post WHERE visible=1");

$post_sql = mysql_query("SELECT postid,threadid,username,userid,dateline FROM vb_post WHERE visible=1 ORDER BY postid DESC $limited");
to
$post_sql = mysql_query("SELECT postid,threadid,username,userid,dateline FROM post WHERE visible=1 ORDER BY postid DESC $limited");

and

$thread_sql = mysql_query("SELECT title FROM vb_thread WHERE threadid=$tid");
to
$thread_sql = mysql_query("SELECT title FROM thread WHERE threadid=$tid");

(pretty much just what tn said).

will this show posts of "secret board" ?

I don't *think* so (the "WHERE visible=1" should prevent non-public posts from showing up, if I understand that database entry correctly), but I haven't actually tested it. Let me know if it doesn't work as intended, and I'll see what I can do. I'll work on the code as well so there's an entry in the "modifiables" section for the database prefix so it's more obvious.

Ron