有时无法加载 css

我又被困住了，需要你的帮助。我有时无法在我的网页上加载 css。实际上，昨天它工作正常，但今天它没有加载。因此，我删除了整个文件夹并上传了另一个我在localhost上使用的文件夹。然后它又工作了一段时间。重新启动浏览器后，我遇到了问题。

以下是有关我的代码的详细信息：

控制器： Users.php ：

<?php
session_start();
class Users extends CI_Controller
{
    public function viewinsert1()
    {
        $this->load->view('createfinal');
    }
    public function viewinsert2()
    {
        $this->load->library('form_validation');
        $this->form_validation->set_rules('email', 'email', 'trim|required|valid_email|xss_clean');
        $this->load->view('personalfinal');
    }
    public function viewinsert3()
    {
        $this->load->view('socialfinal');
    }
    public function viewupdate()
    {
        $this->load->view('view_update');
    }
    public function viewdelete()
    {
        $this->load->view('view_delete');
    }
    public function show()
    {
        // $this->load->model('user_model');
        $data['results'] = $this->user_model->get_users();

        $this->load->view('user_view', $data);
        // foreach ($result as $object) 
        // {
        //  echo $object->id . "</br>"; 
        // }
    }
    // public function insert()
    // {
    //  $username = "Peter";
    //  $password = "12345";
    //  $this->user_model->create_users([
    //      'username' => $username,
    //      'password' => $password
    //      ]);
    // }
    public function insert()
    {
        // echo $this->input->post('password') . "</br>";
        // echo $_POST['username'];

        //echo $email = $this->input->post('email');
        //echo $_SESSION["email"];
        // $email  = $this->input->post('email');

        // $_SESSION["email"] = $email;
        // $_SESSION["pass"] = $pass;
        // $_SESSION["cpass"] = $cpass;
        // $_SESSION["fname"] = $fname;
        // $_SESSION["lname"] = $lname;
        // $_SESSION["phone"] = $phone;
        // $_SESSION["address"] = $address;
        $this->load->library('form_validation');
        $this->form_validation->set_rules('email', 'email', 'trim|required|valid_email|xss_clean');
        $this->form_validation->set_rules('fname', 'firstname', 'trim|alpha|required|xss_clean');
        $this->form_validation->set_rules('lname', 'lastname', 'trim|alpha|required|xss_clean');
        $this->form_validation->set_rules('phone', 'phone', 'trim|numeric|required|integer|exact_length[10]');
        $this->form_validation->set_rules('address', 'address', 'trim|alpha_dash|required');
        $this->form_validation->set_rules('pass', 'cpass', 'trim|required|matches[cpass]|md5');
        $this->form_validation->set_rules('pass', 'cpass', 'trim|required');
        if ($this->form_validation->run() == FALSE)
        {
            $this->load->view('createfinal');
            echo "Error";
        }
        else
        {
            $data = array(
                    'email' => $_SESSION["email"],
                    'firstname' => $_SESSION["fname"],
                    'lastname' => $_SESSION["lname"],
                    'phone' => $_SESSION["phone"],
                    'address' => $_SESSION["address"],
                    'twitter' => $this->input->post('twitter'),
                    'facebook' => $this->input->post('facebook'),
                    'googleplus' => $this->input->post('gplus'),
                    'password' => $_SESSION["pass"],
                    'confirm' => $_SESSION["cpass"], 
                    );
        // echo var_dump($data);

        $result = $this->user_model->create_users($data);
        $this->load->view('createfinal');
        echo "<h1>The data has been inserted</h1>";
        }
    }
    public function update()
    {
        if (isset($_POST['update'])) 
        {
            $id = $this->input->post('id');
            $data = array(
                    'username' => $this->input->post('username'),
                    'password' => $this->input->post('password')
                          );
            $this->user_model->update_users($data, $id);
            echo "<h1> Data is updated successfully:) </h1>";
            $this->load->view('view_update');
        }
        else
        {
            echo "Oops! There is something wrong!";
        }
    }
    public function delete()
    {
        if (isset($_POST['delete'])) 
        {
            $id = $this->input->post('id');
            $this->user_model->delete_users($id);
            echo "<h1>The data has been deleted.</h1>";
        }
        else
        {
            echo "<h3>No Such data exist!</h3>";
        }
    }
}
?>

这是我想加载的视图。.

createfinal.php ：

<!DOCTYPE html>
<html>
<head>
    <title>Login Form</title>
    <link rel="stylesheet" type="text/css" href="<?php echo base_url();?>css/style.css">
</head>
<body>
<!-- multistep form -->
<form id="msform" action="viewinsert2" method="post">
    <!-- progressbar -->
    <ul id="progressbar">
        <li class="active">Account Setup</li>
        <li>Social Profiles</li>
        <li>Personal Details</li>
    </ul>
    <!-- fieldsets -->
    <fieldset>
        <h2 class="fs-title">Create your account</h2>
        <h3 class="fs-subtitle">This is step 1</h3>
        <input type="text" name="email" placeholder="Email" />
        <input type="password" name="pass" placeholder="Password" />
        <input type="password" name="cpass" placeholder="Confirm Password" />
        <input type="submit" name="next" class="next action-button" value="Next" />
    </fieldset>

</body>
</html>

css 文件夹与应用程序文件夹并行。