How to create a 404 page - Page Not Found

Creating an Error 404 Page

If your Theme does not include a file named page_not_found.php, you can create your own.

Create a page_not_found.php

Upload the file to application/themes/CustomThemeFolder (or where your theme is)

Then add the following

<?php
defined('C5_EXECUTE') or die("Access Denied.");
$this->inc('elements/header.php'); ?>

<main>
    <div class="container">
        <div class="row">
            <div class="col-sm-9 col-sm-offset-3">
                <div class="jumbo">
                    <h1><?php echo t('404 Error')?></h1>
                    <p><?php echo t('Page not found.')?></p>
                </div>
            </div>
        </div>
    </div>
</main>

<?php  $this->inc('elements/footer.php'); ?>

If you want to make your 404 page editable with a search, use the following instead.

<?php 
defined('C5_EXECUTE') or die("Access Denied.");
$this->inc('inc/header.php'); ?>

        <div id="main-content" class="main-container">
            <div class="main-content-inner clearfix">
                <main role="main">
                    <div class="container">
                        <div class="row">
                            <div class="col-sm-8 col-sm-offset-2">
<main role="main">
                    <article>
                        <?php  
                        $a = new Area('Main');
                        $a->enableGridContainer();
                        $a->display($c);
                        ?>
                    </article>
                </main>                             
<div class="jumbo">
                                    <h1><?php   echo t('404 Error')?></h1>
                                    <p><?php   echo t('Page not found, so please search.')?></p>

                                    <?php 
                                        $bt = BlockType::getByHandle('search');
                                        $bt->controller->title = t('Search');
                                        $bt->controller->buttonText = t('Search');
                                        $bt->render();
                                    ?>

                                </div>
                            </div>
                        </div>
                    </div>
                </main>
            </div>
        </div>

<?php   $this->inc('inc/footer.php'); ?>

Find out how to optimize you 404 error page.