ZDoom forums has a system in place in which new users' (and Guest posters') first posts will be invisible until a moderator approves them. After your first post is approved, all further posts will always appear immediately. This is a measure to protect the forums from the incessant spam bots that seem to plague us a lot of the time (as well as a preventative measure because a few idiots decided to ruin the fun for everybody else).
So please, if you don't see your post "go through" and appear on the forums, don't double-post it - just be patient and a moderator will likely see and approve your post within an hour (or possibly more). Much like any other moderator-related issue, we can't be available 24/7, so if your post hasn't appeared and you haven't received an email notification about it being approved or disapproved, that does not mean it has been lost.
And further, we'd really appreciate it if you wouldn't make further posts (that go into the approval queue) complaining about your post not having been approved yet. Again, we can't be available 24/7.
Addendum: As of late, we have also been disapproving posts that are breaking the rules or lack any form of common sense. Following the Official ZDoom Forum Rules, particularly the Guidelines section, will go a long way toward making a good enough first impression that your post is approved. Talking in txt-spk lolz and posting things that aren't related to the topic tends to result in a disapproval. Remember, disapproved posts do not mean you will never be approved, it just means you need to try making a different post. Really, though, if your post gets disapproved, pay close attention to the disapproval reason (you'll usually see it as an email message) and take it as a sign that you may need to lurk more.