It takes a lot of hard work to get banned, although some users do it unintentionally. Any way you do it, you're still banned. Being banned might make you scared at first, a bit woozy even. Don't worry; most times it isn't a full account deletion. If you're banned, then your screen will probably look something like this when you log-in:
If your screen looks nothing like that, then chances are, you are not banned.
There is no sure-fire way to immediately unban yourself. Chances are you will just have to wait out your sentence.
If you feel that you have been banned unfairly, simply PMing a super moderator with the reason you think you've been banned unfairly is good enough if you really have been banned unfairly. You may also send an email to firstname.lastname@example.org. However, you should not go onto the forums and complain.
IP bans are for serious offenses.
When you are IP banned, anytime you try to visit a ROBLOX webpage, you will receive an HTTP 403 (Access Denied) error.
NOTE: If your account is IP banned, that ban will stick. So even if you manage to access the Roblox site through another IP address, if you successfully log into the banned account, this new IP will subsequently be banned.
It is believed that IP bans only last two weeks before they expire so that users with dynamic IP addresses do not cause grief with other potential ROBLOX users.