警報型別

不同於像其他一些引導部件的按鈕 ，該通知也沒有拿出一個 default 或 primary 造型，因為他們是為了提醒以特定的方式給使用者。

<div class="alert alert-success" role="alert">
    Some action was completed successfully
</div>
<div class="alert alert-info" role="alert">
    Here is some information. Just FYI.
</div>
<div class="alert alert-warning" role="alert">
    Careful! You're about to do something dangerous.
</div>
<div class="alert alert-danger" role="alert">
    An error (or something dangerous) happened!
</div>