Examples

Wrap any text and an optional dismiss button in .alert and one of the four contextual classes (e.g., .alert-success) for basic alert messages.

No default class

Alerts don't have default classes, only base and modifier classes. A default gray alert doesn't make too much sense, so you're required to specify a type via contextual class. Choose from success, info, warning, or danger.

Hello! Lorem ipsum dolor sit amet, consectetur adipisicing elit.
Well done! You successfully read this important alert message.
Heads up! This alert needs your attention, but it's not super important.
Warning! Better check yourself, you're not looking too good.
Oh snap! Change a few things up and try submitting again. 
<div class="alert alert-black">...</div><div class="alert alert-success">...</div><div class="alert alert-info">...</div><div class="alert alert-warning">...</div><div class="alert alert-danger">...</div>

Dismissable alerts

Build on any alert by adding an optional .alert-dismissable and close button.

Warning! Better check yourself, you're not looking too good. 
<div class="alert alert-warning alert-dismissable"> <button type="button" class="close" data-dismiss="alert" aria-hidden="true">&times;</button> <strong>Warning!</strong> Better check yourself, you're not looking too good.</div>

Ensure proper behavior across all devices

Be sure to use the <button> element with the data-dismiss="alert" data attribute.

Use the .alert-link utility class to quickly provide matching colored links within any alert.

Well done! You successfully read this important alert message.
Heads up! This alert needs your attention, but it's not super important.
Warning! Better check yourself, you're not looking too good.
Oh snap! Change a few things up and try submitting again. 
<div class="alert alert-success"> <a href="#" class="alert-link">...</a></div><div class="alert alert-info"> <a href="#" class="alert-link">...</a></div><div class="alert alert-warning"> <a href="#" class="alert-link">...</a></div><div class="alert alert-danger"> <a href="#" class="alert-link">...</a></div>
Well done! You successfully read this important alert message.
Heads up! This alert needs your attention, but it's not super important.
Warning! Better check yourself, you're not looking too good.
Oh snap! Change a few things up and try submitting again. 
<div class="alert alert-success"> <div class="fa fa-volume-up alert-icon"></div></div><div class="alert alert-info"> <div class="fa fa-tags alert-icon"></div></div><div class="alert alert-warning"> <div class="fa fa-cloud-download alert-icon"></div></div><div class="alert alert-danger"> <div class="fa fa-power-off alert-icon"></div></div>