Admins can block users at Special:Block. These blocks should only be used for the good of the wiki. These blocks can last for various amounts of time, these are stated below. If you are blocked, it may be a mistake and you should contact an admin immediately. You don't have to be a user to be blocked, unidentified users can be and will be blocked where necessary. If you have an account, it doesn't mean you are more likely to be blocked, the length of the block is higher on registered accounts as IP addresses will move. It is very unlikely that you will be blocked and you can't be blocked by accident.
The following holds the guide to the length of blocks admins should adhere to.