类帮助内联的bootstrap无法在模态下工作

Question

我有一个应该以模态显示的表单。但是当我尝试使用help-inline类添加span时。它没有显示我在跨度之间包含的文字。 模态的代码如下：

<div id="clientModal" class="modal hide fade" tabindex="-1" role="dialog" aria-labelledby="clientModalLabel" aria-hidden="true">
                <div class="modal-header">
                    <button type="button" class="close" data-dismiss="modal" aria-hidden="true">X</button>
                    <h3 id="clientModalLabel">Login Form<small class="muted small"> (Client) </small></h3>
                </div>
                <div class="modal-body">
                    <form class="form-horizontal" action="loginScript.php" method="post">
                        <div class="control-group">
                            <label class="control-label" for="username">Username </label>
                            <div class="controls">
                                <input type="text" name="username" placeholder="Username" required autofocus/>
                                <input type="hidden" name="role" placeholder="Role" value="Client"/>
                            </div>
                        </div>
                        <div class="control-group">
                            <label class="control-label" for="password">Password</label>
                            <div class="controls">
                                <input type="password" name="password" placeholder="Password" required/>
                                <span class="help-inline">Incorrect Password</span>    <!-- not Working... -->
                            </div>
                        </div>
                        <div class="control-group">
                            <div class="controls">
                                <input type="submit" class="btn btn-primary" value="Login"/>
                                <input type="button" class="btn btn-link" value="Forgot Password?">
                            </div>
                        </div>
                    </form>
                </div>
            </div>

它的外观如下...... span标记的内容完全不可见

任何帮助将不胜感激......