There are several situations in which you will probably receive notifications from the system:
In case you are banned due to violating one of the game rules and try to construct or do soemthing in your account, you will get an error notification:

The error notification also indicates why your account is banned (in the picture above the account has been banned due to multiaccounting). To solve the issue, you should write a message to the multihunter. You can do this by either writing an IGM to the recipient "Multihunter" or by clicking on "write message" on the error message you see.
In case your account is temporarly banned, you will get the following error notification:

In case this should happen to you, do not worry. This just means you clicked too fast and the issue will be resolved after a few minutes.
In case you tried to open an invalid or restricted page, you will receive an error notification:

The following notifications exist:
In case you try to send away too many messages in a short time you will receive the following error:

It is nothing to worry about. Just wait the respective time shown and the issue will be solved.
Sometimes TRAVIAN needs to give information to all of the players on the server and therefore, a message may be sent to all of them:

Reasons for this could be:
You should read this message carefully and then click on the green "continue" button (marked with the red circle in the picture above). Afterwards you will be able to play again without any restrictions.
In case you have a problem with finding or clicking on the "continue" button just send an email to admin@travian.com.