There are a few cases where content will be removed from view:
1) Content that is illegal.
2) Spam: advertising not authorized, or unsolicited commercial advertising

(Might be more. If so, additional reasons should be added here.)

When there is a different rule violation, your thread or posts may be moved to:
[forum=121]/dev/random[/forum] (User-Joinable: a social forum with much fewer restrictions.)
[forum=7]/dev/null[/forum] (a place for rule violations and junk or flame-festivals. Threads are often closed when moved here. If you want to flame, /dev/random is available, and users can choose to see your content or not.)
[forum=37]Fucktard Hall[/forum] (serious or repeat offenses: users with posts here are usually banned, and their email address often published.)

In order to see "/dev/random" you must choose to subscribe to the "All Social" Usergroup in your UserCP. Occasionally, if your thread is moved to /dev/random, you will be subscribed to All_Social, but this is not guaranteed.