The way you end your error messages can have a big impact on how the user perceives them. Here’s a quick overview of what each type of punctuation says to the reader:

- Period or no punctuation: Simple and direct, the message comes across without any specific tone.

- Question mark: Polite and unintrusive, this is like saying “Perhaps you ought to consider…”

- Exclamation point: Loud and confrontational, this tends to make the message seem like an insult. It should be limited to cases where you need to warn the user about a truly dangerous situation.

- Emoticon: Playful and informal, I’ve never really seen smileys or other emoticons used in error messages. However, I think they can be useful when you’re trying to impart a more casual tone or offer advice.

Although these may seem like subtle differences, they can affect how the user interprets your messages, and ultimately how they feel about your product.