How annoying or useful are warning or alert messages for the users?

1. Which is mostly used to give a warning message to users?
2. What is a warning message?
3. What are two elements that every notification must have?

Which is mostly used to give a warning message to users?

An alert dialog box is mostly used to give a warning message to the users.

What is a warning message?

A warning message is a modal dialog box, in-place message, notification, or balloon that alerts the user of a condition that might cause a problem in the future.

What are two elements that every notification must have?

Relevance and Timeliness. The best way to stay relevant with notifications is good old user data analysis.