Default alert

<div class="alert alert-block fade in">
  <button type="button" class="close" data-dismiss="alert">&times;</button>  
  <strong>Warning!</strong> Best check yo self, you're not looking too good.
</div>

Error or danger

<div class="alert alert-error alert-block fade in">
  <button type="button" class="close" data-dismiss="alert">&times;</button>
  <strong>Oh snap!</strong> Change a few things up and try submitting again. 
</div>

Success

<div class="alert alert-success alert-block fade in">
  <button type="button" class="close" data-dismiss="alert">&times;</button>
  <strong>Well done!</strong> You successfully read this important alert message. 
</div>

Information

<div class="alert alert-info alert-block fade in">
  <button type="button" class="close" data-dismiss="alert">&times;</button>
  <strong>Heads up!</strong> This alert needs your attention, but it's not super important. 
</div>