1.水平表单 ```css <h1 class="text-center popover-header">注册</h1> <form action="" id="myForm" class="col-6 offset-3"> <div class="row form-group"> <label for="" class="col-sm-2 col-form-label">用户名</label> <div class="col-sm-10"> <input type="text" class="form-control"> </div> </div> <div class="row form-group"> <label for="" class="col-sm-2 col-form-label">密码</label> <div class="col-sm-10"> <input type="password" class="form-control"> </div> </div> <div> <button type="submit" class="btn btn-primary ">提交</button> </div> </form> ``` ``` form div class="row form-group" label class="col-sm-2 col-form-label" div class="col-sm-10" input class="form-control" ```