Messages To the User
Response messages to the user should be wrapped in a div or p tag with one of the following three class names assigned.
Use a success message to tell the user that her action has been fulfilled.
<div class="success"Your data has been saved.</div>
An alert message informs the user that something must be corrected.
<div class="alert">Please correct the information below.</div>
Error messages must only be used when the system itself or some of its sub systems failed, not when the user makes a mistake.
<div class="error">This is an error message telling that the application has failed.</div>