<a class="btn btn-default" href="#" rel="external nofollow" role="button">Link</a>
<button class="btn btn-default" type="submit">Button</button>
<input class="btn btn-default" type="button" value="Input">
<input class="btn btn-default" type="submit" value="Submit">

<!-- Standard button -->
<button type="button" class="btn btn-default">Default</button>
<!-- Provides extra visual weight and identifies the primary action in a set of buttons -->
<button type="button" class="btn btn-primary">Primary</button>
<!-- Indicates a successful or positive action -->
<button type="button" class="btn btn-success">Success</button>
<!-- Contextual button for informational alert messages -->
<button type="button" class="btn btn-info">Info</button>
<!-- Indicates caution should be taken with this action -->
<button type="button" class="btn btn-warning">Warning</button>
<!-- Indicates a dangerous or potentially negative action -->
<button type="button" class="btn btn-danger">Danger</button>
<!-- Deemphasize a button by making it look like a link while maintaining button behavior -->
<button type="button" class="btn btn-link">Link</button>

<p>
 <button type="button" class="btn btn-primary btn-lg">Large button</button>
 <button type="button" class="btn btn-default btn-lg">Large button</button>
</p>
<p>
 <button type="button" class="btn btn-primary">Default button</button>
 <button type="button" class="btn btn-default">Default button</button>
</p>
<p>
 <button type="button" class="btn btn-primary btn-sm">Small button</button>
 <button type="button" class="btn btn-default btn-sm">Small button</button>
</p>
<p>
 <button type="button" class="btn btn-primary btn-xs">Extra small button</button>
 <button type="button" class="btn btn-default btn-xs">Extra small button</button>
</p>

<button type="button" class="btn btn-primary btn-lg btn-block">Block level button</button>
<button type="button" class="btn btn-default btn-lg btn-block">Block level button</button>

<button type="button" class="btn btn-primary btn-lg active">Primary button</button>
<button type="button" class="btn btn-default btn-lg active">Button</button>

<button type="button" class="btn btn-lg btn-primary" disabled="disabled">Primary button</button>
<button type="button" class="btn btn-default btn-lg" disabled="disabled">Button</button>