You likely somehow didn't do something. That would be my first thought.
If it wasn't acceptable, the Moderators would close it, and if it was REALLY bad, they'd ban You, but the Mod's here are pretty good guys. As long as it's FireArms Related, clean and at least FAIRLY meaningful, it's usually no problem at all.
"Online Guns at 18" shouldn't be unacceptable. Try it again.
Me personally, I've had a few small problems in the last few days, with replies/posts, here. Capitol letters won't stay caps, has been the main problem, so You MAY be getting a little website problem, but just try Your Thread again.
Or, keep in mind that the Moderators Screen Name's are BOLD Blue letters, while all others are a bit "finer", not so distinct, so if/when You see one of them online, You can click on their Name and send them a message. Let them know what problem You're having, and they'll address it from there. If nothing else, they'll guide You through the process of starting a Thread, or they may know of an existing problem.
And, when one of the Moderators see this Thread, they'll likely chime in.