按钮(补充)
(ps:居中元素可以使用<center></center>标签)
块级按钮(ps:按钮占一整行)
<button class="btn btn-primary btn-lg btn-block" type="button">大型按钮.btn-lg</button> <button class="btn btn-primary btn-block" type="button">正常按钮</button> <button class="btn btn-primary btn-sm btn-block" type="button">小型按钮.btn-sm</button> <button class="btn btn-primary btn-xs btn-block" type="button">超小型按钮.btn-xs</button>
(ps:元素变块级的属性:block。class="btn-block" )