Using color to add meaning only provides a visual indication, which will not be conveyed to users of assistive technologies – such as screen readers. Ensure that information denoted by the color is either obvious from the content itself (e.g. the visible text), or is included through alternative means, such as additional text hidden with the .sr-only class.
Add a dismiss button and the .alert-dismissible class, which adds extra padding to the right of the alert and positions the .close button.
To animate alerts when dismissing them, be sure to add the .fade and .show classes.