Css and bootstrap in yii2
<p>I'm quite new to Yii2 and I have created a layout page, but my CSS doesn't work fully. It only loads parts of it. Can somebody help me please?</p>

<p>My layout:</p>

<pre><code>&lt;?php
namespace app\views\layouts;

use yii\bootstrap\Alert;
use yii\bootstrap\ActiveForm;
use yii\helpers\Url;
use yii\helpers\Html;
use yii\bootstrap\NavBar;
use yii\bootstrap\Button;
use app\models\Search;
use yii\bootstrap\Nav;
use app\assets\AppAsset;
use app\models\LoginForm;
use yii\web\View;
use Yii;

AppAsset::register($this);
?&gt;
&lt;?php $this-&gt;beginPage() ?&gt;
&lt;!DOCTYPE html&gt;
&lt;html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"&gt;
&lt;head&gt;
    &lt;meta http-equiv="Content-Type" content="text/html; charset=utf-8" /&gt;
    &lt;meta name="language" content="en" /&gt;
    &lt;?= Html::csrfMetaTags() ?&gt;
    &lt;title&gt;&lt;?php echo Html::encode($this-&gt;title); ?&gt;&lt;/title&gt;

    &lt;link rel="shortcut icon" href="&lt;?php echo Yii::getAlias('@web/themes/dcu') ?&gt;/assets/images/favicon.png" type="image/x-icon" /&gt;


     &lt;link rel="stylesheet" type="text/css" href="&lt;?php echo Yii::getAlias('@web'); ?&gt;/themes/dcu/assets/css/bootstrap.css" /&gt;
    &lt;link rel="stylesheet" type="text/css" href="&lt;?php echo Yii::getAlias('@web'); ?&gt;/themes/dcu/assets/css/bootstrap-responsive.min.css" /&gt;
       &lt;link rel="stylesheet" type="text/css" href="&lt;?php echo Yii::getAlias('@web'); ?&gt;/themes/dcu/assets/css/gbu.csss" /&gt;
        &lt;link rel="stylesheet" type="text/css" href="&lt;?php echo Yii::getAlias('@web'); ?&gt;/themes/dcu/assets/css/font-awesome.css" /&gt;

&lt;?php $this-&gt;head()?&gt;
&lt;/head&gt;
&lt;body&gt;
    &lt;?php $this-&gt;beginBody() ?&gt;
    &lt;span class="striept"&gt;&lt;/span&gt;
    &lt;div id="wrap"&gt;
        &lt;div class="container" id="page"&gt;
            &lt;div class="row header"&gt;
                &lt;div class="span7"&gt;
                    &lt;a href=&lt;?php Yii::$app-&gt;homeUrl ?&gt;&gt;&lt;img src="&lt;?php echo Yii::getAlias('@web'); ?&gt;/themes/dcu/assets/images/documentatiecentrum-urk.png" /&gt;&lt;/a&gt;
                &lt;/div&gt;
                &lt;div class="span5 login-form"&gt;
                    &lt;?php if (Yii::$app-&gt;user-&gt;isGuest): ?&gt;
                        &lt;div class="form"&gt;
                        &lt;/div&gt;
                    &lt;?php else: ?&gt;
                        &lt;ul class="inline"&gt;
                            &lt;li&gt;Je bent inlogd als: &lt;?php echo Yii::$app-&gt;user-&gt;identity-&gt;username; ?&gt; &lt;/li&gt;
                            &lt;li&gt;
                            &lt;/li&gt;
                        &lt;/ul&gt;
                    &lt;?php endif; ?&gt;
                &lt;/div&gt;
            &lt;/div&gt;
            &lt;div class="row"&gt;
                &lt;div class="span12 zoeken"&gt;
                    &lt;div class="input-append"&gt;

                    &lt;/div&gt;
                &lt;/div&gt;
            &lt;/div&gt;

        &lt;/div&gt;

        &lt;div class="container-fluid dark topmargin"&gt;
            &lt;div class="container"&gt;
                &lt;div class="row"&gt;
                    &lt;div class="span8"&gt;
                        &lt;h3&gt;Onze partners&lt;/h3&gt;
                        &lt;div class="row-fluid"&gt;
                            &lt;div class="span4"&gt;

                            &lt;/div&gt;
                            &lt;div class="span4"&gt;

                            &lt;/div&gt;
                            &lt;div class="span4"&gt;

                            &lt;/div&gt;
                        &lt;/div&gt;
                    &lt;/div&gt;
                    &lt;div class="span4"&gt;
                        &lt;div class="row-fluid"&gt;
                            &lt;h3&gt;Ook meehelpen?&lt;/h3&gt;
                            &lt;p&gt;Met uw steun zorgt u er samen met ons voor dat ons grote cultuurbezit, 'oenze taol', blijft bestaan!&lt;/p&gt;&lt;p&gt;Steun ons project en doneer een bedrag op onze bankrekening: 11.40.24.820 Rabobank Urk. Bedankt voor uw hulp!&lt;/p&gt;
                            &lt;a class="btn btn-primary" href="https://www.justgiving.nl/nl/charities/83-stichting-%20urker-taol" target="_new"&gt;Direct doneren&lt;/a&gt;
                            &lt;a class="btn btn-primary" href="&lt;?php echo Yii::$app-&gt;basePath; ?&gt;donateursformulier.pdf" target="_new"&gt;Donateursformulier&lt;/a&gt;
                        &lt;/div&gt;
                    &lt;/div&gt;
                &lt;/div&gt;
                &lt;div class="row"&gt;
                    &lt;div class="span12 copyright"&gt;
                    &lt;/div&gt;
                &lt;/div&gt;
            &lt;/div&gt;
        &lt;/div&gt;
    &lt;/div&gt;
   &lt;/body&gt;
    &lt;?php $this-&gt;endBody() ?&gt;
&lt;/html&gt;
&lt;?php $this-&gt;endPage() ?&gt;
</code></pre>

<p>I think the problem is the bootsrap, because all the other CSS files are all OK.</p>