"An account starts off with 0 out of 10 black marks, but this may increase if the player breaks the rules. The account is in the green zone if it has no black marks, though changes through yellow, orange and red as offences accumulate. The black marks and the zone can change suddenly if the player commits serious offences.
Offenders may be banned or just muted, and either may be temporary (for example, for 24 hours) or permanent... [B]anned players are unable to log into the game at all. Players who are banned are also not allowed to vote in polls.
Generally, players are permanently banned after 10 blackmarks. But if certain appeals are made, players may result in more. You will be on a last chance, in which case any more offences will get you permanently banned, unless another last chance appeal is made."
"Bans from the RuneScape Forums are for essentially similar reasons to those in-game. However, they also include flaming and spamming; while spamming in-game is an offence, many players do not realise this and it often goes unreported.
If a player is muted or banned from the game, they are also automatically banned from the forums."