Be careful of making jokes. Be especially careful of using irony or sarcasm.
Remember, the person reading your message cannot see your face and cannot hear your voice. In other words, they cannot see your smile, they cannot hear your laugh, they cannot see your wink.
A careless comment can lead to serious misunderstanding.
If you real need to use humour or irony, make it clear by adding a smiley at the end of the sentence, or on/off toggles at the beginning and end of longer passages. For examples of smileys and toggles, refer to the Smiley Page.